Translation update for 0.7.1

There was also a new translation available, "ja" (Japanese), however
almost nothing was filled in yet, so I'm not including it for this release.

Also clarify translation process that the package `gettext` is needed to run string extractor.

Issue 1884: Add a backup warning to the encryptwallet RPC command

This reverts commit 14ac0adc.

Windows: fix URI association setting in registry

Arbitrary numbers of test vectors can be generated using the script
`gen_base58_test_vectors.py`.

Don't include HTML in translation strings. Do split the huge message over several lines.

Prettier lines

harmonize printf format characters

- remove the "%" character from format characters for (s)size_t and
  ptrdiff_t and harmonize them with the ones for int64 and uint64

- fix for #1877
- fix was reported to work via
  https://bitcointalk.org/index.php?topic=110243.msg1230418#msg1230418

Fix compilation with clang under OS X

Removed a duplicated identical if

switch to Qt 4.8.2 for Windows builds

Update to use OpenSSL 1.0.1c

Remove stack randomization

walletdb.h: remove dead code

Fix: when testnet=1 specified, change default RPC port to 18332

As the code was before, toHTML added empty elements to mapValue to check for their existance. Now first it check for their existance and then for their non-emptiness.

Removed a duplicated identical if

There are two equal ifs, one inside another. If the first one is true, then the second one is true.

Documented bug in sign-extension behavior of opcodes OP_AND, OP_OR, and OP_XOR

Previously, trying to compile with clang would result in the error: assigning to 'objc_object *' from incompatible type 'DockIconClickEventHandler *'

commit 5a1a3622 effectively enabled these warnings, but they need
to be fixed before being enabled in the general build scripts.

Add printf-style warnings to strprintf() and OutputDebugStringF()

Due to a bug in the implementation of MakeSameSize(), using OP_AND, OP_OR, or OP_XOR with signed values of unequal size will result in the sign-value becoming part of the smaller integer, with nonsensical results. This patch documents the unexpected behavior and provides the basis of a solution should decision be made to fix the bug in the future.

Import $DataDir/bootstrap.dat automatically, if it exists.

change last occurance of mac to macx in Qt project-file

Compile/link Bitcoin-Qt.app with -pthread on OSX

Bitcoin-Qt: expand GCC Stack-Smashing Protector usage (non Windows)

additional fix for #1843