Fix makefile.linux-mingw

Yes, we might release as v0.4, but let's just do a simple increment
for now.

Warning fixes

Only declare & define SigIllHandlerSSE2 when its used.
Signed-off-by: Giel van Schijndel <me@mortis.eu>

Remove several unused variables.
Signed-off-by: Giel van Schijndel <me@mortis.eu>

Add default cases to opcode switches to assert that they should never
occur.
Signed-off-by: Giel van Schijndel <me@mortis.eu>

Don't check for a negative parameter count, because not only will it
never happen, it doesn't make any sense either.

Invalid sockets (as returned by socket(2)) are always exactly -1 (not
just negative as negative file descriptors are technically not
prohibited by POSIX) on POSIX systems.  Since we store them in SOCKET
(unsigned int), however, that really is ~0U (or MAX_UINT) which happens
to be what INVALID_SOCKET is already defined to, so an additional check
for being negative is not only unnecessary (unsigned integers aren't
*ever* negative) its redundant as well (the INVALID_SOCKET comparison is
enough).
Signed-off-by: Giel van Schijndel <me@mortis.eu>

Don't unnecessarily assign to variables within the *boolean* expression
of a conditional.
Signed-off-by: Giel van Schijndel <me@mortis.eu>

In the assert()s take advantage of the fact that string constants
("string") are effectively of type 'const char []', which when used in
an expression yield a non-NULL pointer.

An assertion that should always fail can thus be formulated as:
  assert(!"fail);

An assertion where a text message should be added to the expression can
be written as such:
  assert("message" && expression);
Signed-off-by: Giel van Schijndel <me@mortis.eu>

fix warning on 64bit systems: cast to pointer from integer of different size [-Wint-to-pointer-cast]
Signed-off-by: Giel van Schijndel <me@mortis.eu>

Add minversion to wallet.

High resolution Windows icon

Add bitcoin.org logos/branding to NSIS installer.

Wallet Private Key Encryption (on CWallet)

The .ico file has changed in the following ways:
* Added 64x64 layer (max size for "Classic Mode").
* Added 256x256 layer (max size for Vista and 7).
* Removed copies with no alpha channel:
  * Display depths lower than 32-bits are rare nowadays.
  * 8-bit alpha channels in icons has been supported since XP.
  * If the display depth is lowered, they look no better than the
    downsampled versions that Windows automatically generates.

Tested various sizes on both XP and Win 7. It looks fine
(unchanged) on XP and downright sexy on Win 7.

This prevents old clients from opening, and thus corrupting
or otherwise causing harm to encrypted wallets.

This speeds up the encryption process significantly.

This commit adds support for ckeys, or enCrypted private keys, to the wallet.
All keys are stored in memory in their encrypted form and thus the passphrase
is required from the user to spend coins, or to create new addresses.

Keys are encrypted with AES-256-CBC using OpenSSL's EVP library. The key is
calculated via EVP_BytesToKey using SHA512 with (by default) 25000 rounds and
a random salt.

By default, the user's wallet remains unencrypted until they call the RPC
command encryptwallet <passphrase> or, from the GUI menu, Options->
Encrypt Wallet.

When the user is attempting to call RPC functions which require the password
to unlock the wallet, an error will be returned unless they call
walletpassphrase <passphrase> <time to keep key in memory> first.

A keypoolrefill command has been added which tops up the users keypool
(requiring the passphrase via walletpassphrase first).
keypoolsize has been added to the output of getinfo to show the user the
number of keys left before they need to specify their passphrase (and call
keypoolrefill).

Note that walletpassphrase will automatically fill keypool in a separate
thread which it spawns when the passphrase is set. This could cause some
delays in other threads waiting for locks on the wallet passphrase, including
one which could cause the passphrase to be stored longer than expected,
however it will not allow the passphrase to be used longer than expected as
ThreadCleanWalletPassphrase will attempt to get a lock on the key as soon
as the specified lock time has arrived.

When the keypool runs out (and wallet is locked) GetOrReuseKeyFromPool
returns vchDefaultKey, meaning miners may start to generate many blocks to
vchDefaultKey instead of a new key each time.

A walletpassphrasechange <oldpassphrase> <newpassphrase> has been added to
allow the user to change their password via RPC.

Whenever keying material (unencrypted private keys, the user's passphrase,
the wallet's AES key) is stored unencrypted in memory, any reasonable attempt
is made to mlock/VirtualLock that memory before storing the keying material.
This is not true in several (commented) cases where mlock/VirtualLocking the
memory is not possible.

Although encryption of private keys in memory can be very useful on desktop
systems (as some small amount of protection against stupid viruses), on an
RPC server, the password is entered fairly insecurely. Thus, the only main
advantage encryption has for RPC servers is for RPC servers that do not spend
coins, except in rare cases, eg. a webserver of a merchant which only receives
payment except for cases of manual intervention.

Thanks to jgarzik for the original patch and sipa, gmaxwell and many others
for all their input.

Conflicts:

	src/wallet.cpp

Use of LZMA (versus the current zlib) shaves a few MB off the installer.

Remove another magic number: change threshold for nLockTime to constant

Minor translation changes for latest build (Swedish)

Inline comment and idea come from the encprivkeys branch
by Matt Corallo <matt@bluematt.me>.

Fix synchronization of default key

Fix UPnP building, entirely my fault.