P2P: Do not request blocks from peers with fewer blocks than us

Fat-fingered on github, and merged this too early.

This reverts commit 22f9b069.

Send 'mempool' P2P command at the start of each P2P session

Before, opening a -datadir that was created with a new
version of Berkeley DB would result in an un-caught DB_RUNRECOVERY
exception.

After these changes, the error is caught and the user is told
that there is a problem and is told how to try to recover from
it.

add LOCK() for proxy related data-structures

Send --help message to stdout i.s.o stderr

When datadir missing, show messagebox instead of printing error to stderr

Document RPC error codes

Replace all "magic values" in RPCError(...) by constants.

Translation update for 0.7.1

- fix #1560 by properly locking proxy related data-structures
- update GetProxy() and introduce GetNameProxy() to be able to use a
  thread-safe local copy from proxyInfo and nameproxyInfo
- update usage of GetProxy() all over the source to match the new
  behaviour, as it now fills a full proxyType object
- rename GetNameProxy() into HaveNameProxy() to be more clear

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.

This allows fun stuff such as `bitcoin --help | less`, and more
easy piping to files.

Looking at other tools such as bash, gcc, they all send their help
text to stdout.

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.