remove FIRST_CLASS_MESSAGING support from the client

- removes the FIRST_CLASS_MESSAGING support from the client, which was no
  default setting anyway
Qt: re-order GUI code

- re-order Qt Actions and connect() calls to match the real GUI layout,
  which makes things easier to read and understand
- remove signMessageAction and verifyMessageAction from tabGroup as we
  didn't use them anyway (as tooltips are not displayed in the menu remove
  these too)
- update 2 comments
Improve RPC console key event behaviour

- Paging using PageUp / PageDown now works when entry widget has focus
- Typing or pasting while the messages widget has focus auto-selects entry widget
Update gitignore and Makefiles for build.h move from src/ to src/obj
Merge pull request #1810 from laanwj/2012_09_rpcconsole_eventfilter

Improve RPC console key event behaviour
Merge pull request #1705 from Diapolo/cleanup_bitcoingui

Qt: re-order GUI code and remove FIRST_CLASS_MESSAGING
Check for canonical public keys and signatures

Only enabled inside tests for now.
Do not forward 0-writes to SHA256
Import LevelDB 1.5, it will be used for the transaction database.
Leveldb Windows port by Edouard Alligand, adapted for MingW by me.
Disable libsnappy detection in LevelDB
Do not force -std=c++0x for MingW builds
Makefile integration of LevelDB
Compact serialization for variable-length integers

Variable-length integers: bytes are a MSB base-128 encoding of the number.
The high bit in each byte signifies whether another digit follows. To make
the encoding is one-to-one, one is subtracted from all but the last digit.
Thus, the byte sequence a[] with length len, where all but the last byte
has bit 128 set, encodes the number:

  a[len-1] & 0x7F) + sum(i=1..len-1, 128^i*((a[len-i-1] & 0x7F)+1))

Properties:
* Very small (0-127: 1 byte, 128-16511: 2 bytes, 16512-2113663: 3 bytes)
* Every integer has exactly one encoding
* Encoding does not depend on size of original integer type
* Encoding preserves ordering (lexicographic order of encoded forms
  corresponds to numeric order of integers)
Compact serialization for variable-length integers: tests
Add CCoins: pruned list of transaction outputs

The CCoins class represents a pruned set of transaction outputs from
a given transaction. It only retains information about its height in
the block chain, whether it was a coinbase transaction, and its
unspent outputs (script + amount).

It has a custom serializer that has very low redundancy.
Compact serialization for scripts

Special serializers for script which detect common cases and encode
them much more efficiently. 3 special cases are defined:
* Pay to pubkey hash (encoded as 21 bytes)
* Pay to script hash (encoded as 21 bytes)
* Pay to pubkey starting with 0x02, 0x03 or 0x04 (encoded as 33 bytes)

Other scripts up to 121 bytes require 1 byte + script length. Above
that, scripts up to 16505 bytes require 2 bytes + script length.
Compact serialization for amounts

Special serializer/deserializer for amount values. It is optimized for
values which have few non-zero digits in decimal representation. Most
amounts currently in the txout set take only 1 or 2 bytes to
represent.
Compact serialization for amounts: tests

Test cases to verify the correctness of the custom amount serializer.
Add CTxUndo: transaction undo information

The CTxUndo class encapsulates data necessary to undo the effects of
a transaction on the txout set, namely the previous outputs consumed
by it (script + amount).