Straight refactor, so mapAddressBook stores a CAddressBookData
(which just contains a std::string) instead of a std::string.

Preparation for payment protocol work, which will add the notion
of refund addresses to the address book.

Replace the loop macro with while (true). The #define caused
problems for Qt.

Also, GetKeyPoolSize() now returns an accurate type, unsigned int.

Compute safe lower bounds on the birth times of all wallet keys. For
pool keys or keys with metadata, the actually stored birth time is
used. For all others, the birth times are inferred from the wallet
transactions.

Refactor keytime:
* Key metadata is kept in a CWallet::mapKeyMetadata (std::map<CKeyId,CKeyMetadata>).
* When generating a new key, time is put in that map, and new key is written.
* AddKeyPubKey and AddCryptedKey do not take a creation time argument, but instead
  pull it from that map, if it exists there.

Bugfix:
* AddKeyPubKey and AddCryptedKey in CWallet didn't override the CKeyStore
  definition anymore. This is fixed, as they no longed need the nCreationTime
  argument now.

Also a few related other changes:
* Metadata can be overwritten.
* Only GenerateNewKey calls GetTime(), as it's the only place where we know for
  sure a key was not constructed earlier.
* When the nTimeFirstKey is known to be inaccurate, it is set to the value 1
  (instead of 0, which would mean unknown).
* Use CPubKey instead of std::vector<unsigned char> where possible.

This (nearly) doesn't change fee rules at all:
 * To make it into the fee transaction area, the dPriority comparison
   changed from < to <=
 * We now just ignore transactions > MAX_BLOCK_SIZE/4 instead of
   doing some calculations to require increasingly large fees as
   size increases.

This also encapsulate wallet-read state information into CWalletScanState.

Removed AreInputsStandard from CTransaction, made it a regular function in main.
Moved CTransaction::GetOutputFor to CCoinsViewCache.

Moved GetLegacySigOpCount and GetP2SHSigOpCount out of CTransaction into regular functions in main.

Moved GetValueIn and HaveInputs from CTransaction into CCoinsViewCache.

Moved AllowFree, ClientCheckInputs, CheckInputs, UpdateCoins, and CheckTransaction out of CTransaction and into main.

Moved IsStandard and IsFinal out of CTransaction and put them in main as IsStandardTx and IsFinalTx. Moved GetValueOut out of CTransaction into main. Moved CTxIn, CTxOut, and CTransaction into core.

Added minimum fee parameter to CTxOut::IsDust() temporarily until CTransaction is moved to core.h so that CTxOut needn't know about CTransaction.

Remove the pnext pointer in CBlockIndex, and replace it with a
vBlockIndexByHeight vector (no effect on memory usage). pnext can
now be replaced by vBlockIndexByHeight[nHeight+1], but
FindBlockByHeight becomes constant-time.

This also means the entire mapBlockIndex structure and the block
index entries in it become purely blocktree-related data, and
independent from the currently active chain, potentially allowing
them to be protected by separate mutexes in the future.

New method in bitcoinrpc:  RunLater, that uses a map of deadline
timers to run a function later.

Behavior of walletpassphrase is changed; before, calling
walletpassphrase again before the lock timeout passed
would result in: Error: Wallet is already unlocked.

You would have to call lockwallet before walletpassphrase.

Now: the last walletpassphrase with correct password
wins, and overrides any previous timeout.

Fixes issue# 1961 which was caused by spawning too many threads.

Test plan:

Start with encrypted wallet, password 'foo'
NOTE:
 python -c 'import time; print("%d"%time.time())'
... will tell you current unix timestamp.

Try:

walletpassphrase foo 600
getinfo
EXPECT: unlocked_until is about 10 minutes in the future

walletpassphrase foo 1
sleep 2
sendtoaddress mun74Bvba3B1PF2YkrF4NsgcJwHXXh12LF 11
EXPECT: Error: Please enter the wallet passphrase with walletpassphrase first.

walletpassphrase foo 600
walletpassphrase foo 0
getinfo
EXPECT: wallet is locked (unlocked_until is 0)

walletpassphrase foo 10
walletpassphrase foo 600
getinfo
EXPECT: wallet is unlocked until 10 minutes in future

walletpassphrase foo 60
walletpassphrase bar 600
EXPECT: Error, incorrect passphrase
getinfo
EXPECT: wallet still scheduled to lock 60 seconds from first (successful) walletpassphrase

Allow setting of MIN_TX_FEE / MIN_RELAY_TX_FEE with
-mintxfee / -mintxrelayfee

Default values are the same (0.0001 BTC).

When debugging another issue, I found a hang-during-startup race condition due to
LoadWallet calling SetMinVersion (via LoadCryptedKey).

Writing to the file that you're in the process of reading is a bad idea.

This solves the issue where no default key can be added after -salvagewallet.

This fixes test_bitcoin failures on openbsd reported by dhill on IRC.

  On some systems rand() is a simple LCG over 2^31 and so it produces
an even-odd sequence.  ApproximateBestSubset was only using the least
significant bit and so every run of the iterative solver would be the
same for some inputs, resulting in some pretty dumb decisions.

Using something other than the least significant bit would paper over
the issue but who knows what other way a system's rand() might get us
here.  Instead we use an internal RNG with a period of something like
2^60 which is well behaved.  This also makes it possible to make the
selection deterministic for the tests, if we wanted to implement that.

Extremely large transactions with lots of inputs can cost the network
almost as much to process as they cost the sender in fees.

We would never create transactions larger than 100K big; this change
makes transactions larger than 100K non-standard, so they are not
relayed/mined by default. This is most important for miners that might
create blocks larger than 250K big, who could be vulnerable to a
make-your-blocks-so-expensive-to-verify-they-get-orphaned attack.

Two changes:

Use IsConfirmed() instead of IsFinal(), so 'getbalance "*" 0' uses the same
'is this output spendable' criteria as 'getbalance'. Fixes issue #172.

And a tiny refactor to CWallet::GetBalance() (redundant call to IsFinal -- IsConfirmed
calls IsFinal).
getbalance with no arguments and 'getbalance "*" 0' could return different different results,

Fixes issue #2178 : attacker could penny-flood with invalid-signature
transactions to deduce which addresses belonged to your node.

I'm committing this early for code review; I still need to write up
a test plan.

Executive summary of fix: check all transactions received from the network
for penny-flood rate-limiting before adding to the memory pool. But do NOT
ratelimit transactions added to the memory pool:
  - because of blockchain reorgs
  - stored in the wallet and added at startup
  - sent from the GUI or one of the send* RPC commands (CWallet::CommitTransaction)

The limit-free-transactions code really should be a method on CNode, with
counters per-peer. But that is a bigger change for another day.

  If the user was really after the fastest possible confirmation times
they would be manually setting a fee. In cases where the wallet builds
a transaction with a priority that is too low to qualify as free until
the next block, go ahead without a fee.  Confirmation frequently takes
multiple blocks even when a minimum fee is provided.

This avoids a potential crash when trying to read the scrippubkeys on
transactions where the first input IsMine but some of the rest are not
when running listaddressgroupings.

- remove unused parameter from ThreadSafeAskFee(), which also results in
  the removal of an orphan translation-string

and associated RPC "listlockunspent".

This is a memory-only filter, which is empty when a node restarts.

Cleaner and removes the need for the application-specific flags in
serialize.h.

It seemed to create two CWalletDB objects that both grab the
database lock.

The original test (checking whether the transaction occurs in the
txindex) is not usable anymore, as it will miss anything already
fully spent. However, as merkle transactions (and by extension,
wallet transactions) track which block they were last seen being
included in, we can use that to determine the need for
rebroadcasting.