Signed-off-by: Johnathan Corgan <johnathan@corganlabs.com>

Assume that when a wallet transaction has a valid block hash and transaction position
in it, the transaction is actually there. We're already trusting wallet data in a
much more fundamental way anyway.

To prevent backward compatibility issues, a new record is used for storing the
block locator in the wallet. Old wallets will see a wallet file synchronized up
to the genesis block, and rescan automatically.

It's unclear if people are using this and if it's worth maintaining.

These changes decode valid SIGHASH types on signatures in assembly (asm) representations of scriptSig scripts.
This squashed commit incorporates substantial helpful feedback from jtimon, laanwj, and sipa.

Add a section "low level RPC API changes" so that the changes with
regard to error codes can be added later.

... in preparation for 0.12

Add information about further notable changes:

- Big endian support
- Memory usage optimization
- Disable wallet transaction broadcast
- Stream isolation for Tor

I dropped mention of libgmp that I had in my first draft because
it looks like we'll be able to get that out prior to release.

Start the RPC server before doing all the (expensive) startup
initialisations like loading the block index.  Until the node is ready,
return all calls immediately with a new error signalling "in warmup"
with an appropriate status message (similar to the init message).

This is useful for RPC clients to know that the server is there (e. g.,
they don't have to start it) but not yet available.  It is used in
Namecoin and Huntercoin already for some time, and there exists a UI
hooked onto the RPC interface that actively uses this to its advantage.

This reverts commit 9fa53dd3.

This reverts commit 7a19efe0.

The wallet now uses the mempool fee estimator with a new
command-line option: -txconfirmtarget (default: 1) instead
of using hard-coded fees or priorities.

A new bitcoind that hasn't seen enough transactions to estimate
will fall back to the old hard-coded minimum priority or
transaction fee.

-paytxfee option overrides -txconfirmtarget.

Relaying and mining code isn't changed.

For Qt, the coin control dialog now uses priority estimates to
label transaction priority (instead of hard-coded constants);
unspent outputs were consistently labeled with a much higher
priority than is justified by the free transactions actually
being accepted into blocks.

I did not implement any GUI for setting -txconfirmtarget; I would
suggest getting rid of the "Pay transaction fee" GUI and replace
it with either "target number of confirmations" or maybe
a "faster confirmation <--> lower fee" slider or select box.

New RPC methods: return an estimate of the fee (or priority) a
transaction needs to be likely to confirm in a given number of
blocks.

Mike Hearn created the first version of this method for estimating fees.
It works as follows:

For transactions that took 1 to N (I picked N=25) blocks to confirm,
keep N buckets with at most 100 entries in each recording the
fees-per-kilobyte paid by those transactions.

(separate buckets are kept for transactions that confirmed because
they are high-priority)

The buckets are filled as blocks are found, and are saved/restored
in a new fee_estiamtes.dat file in the data directory.

A few variations on Mike's initial scheme:

To estimate the fee needed for a transaction to confirm in X buckets,
all of the samples in all of the buckets are used and a median of
all of the data is used to make the estimate. For example, imagine
25 buckets each containing the full 100 entries. Those 2,500 samples
are sorted, and the estimate of the fee needed to confirm in the very
next block is the 50'th-highest-fee-entry in that sorted list; the
estimate of the fee needed to confirm in the next two blocks is the
150'th-highest-fee-entry, etc.

That algorithm has the nice property that estimates of how much fee
you need to pay to get confirmed in block N will always be greater
than or equal to the estimate for block N+1. It would clearly be wrong
to say "pay 11 uBTC and you'll get confirmed in 3 blocks, but pay
12 uBTC and it will take LONGER".

A single block will not contribute more than 10 entries to any one
bucket, so a single miner and a large block cannot overwhelm
the estimates.

Now that 0.9 is branched off, the new release notes for 0.10 or 0.11 or
1.0 should be added here.

Edits to preliminary 0.9.0 release notes should be made in the 0.9.0 branch.

Also add a note to the release notes.
Fixes #3672.

Add all known release notes for versions since 0.3.12,
thanks to Matt Corallo for collecting them on the wiki.

Version numbers changed from 0.7.99 to 0.8.0
Set CLIENT_VERSION_IS_RELEASE to remove pre-release warning
Updated copyright in COPYING and doc/READMEs to 2013
Updated doc/release-notes.txt