Bump version numbers for 0.9.2 branch split-off

Show version as 0.9.1.99 until rc1.
fixes #4163

Rebased-by: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-from: 90fd873
Switch stdout to line buffering

Use line buffering (instead of block buffering) so that messages arrive
immediately in systemd-journald, tail -f debug.log, and the like.

Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-From: 283e405
Squashed 'src/leveldb/' changes from 9094c7f..7924331

42dcc7e Merge upstream LevelDB 1.17.
e353fbc Release LevelDB 1.17
269fc6c Release LevelDB 1.16
REVERT: 9094c7f Temporarily revert to writing .sst files instead of .ldb

git-subtree-dir: src/leveldb
git-subtree-split: 79243314e40ac31d79c68e5658a1d6a64800d50b
Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-From: 938b689
Remove dummy PRIszX macros for formatting

Size specifiers are no longer needed now that we use typesafe tinyformat
for string formatting, instead of the system's sprintf.

No functional changes.

This continues the work in #3735.

Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-From: 783b182
Move base58.h implementation code to base58.cpp

Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-From: f6b7c64
rpc: pass errors from async_accept

According to the [boost::asio documentation](http://www.boost.org/doc/libs/1_55_0/doc/html/boost_asio/reference/basic_socket_acceptor/async_accept/overload2.html),
the function signature of the handler must be:

    void handler(
      const boost::system::error_code& error // Result of operation.
    );

We were binding *all* the arguments, instead of all but the error,
resulting in nullary function that never got the error. Fix this
by adding an input argument substitution.

Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-From: 0a0cd34
rpc: Make sure conn object is always cleaned up

Make sure conn object always gets cleaned up by using a
`boost::shared_ptr`.

This makes valgrind happy - before this commit, one connection object
always leaked at shutdown, as well as can avoid other leaks, when
for example an exception happens.

Also add an explicit Close() to the !ClientAllowed path to make it similar
to the normal path (I'm not sure whether it is needed, but it
can't hurt).

Rebased-By: Wladimir J. van der Laan
Rebased-From: 1a44522
doc: remove mention of `-rpctimeout` from man page

That option hasn't existed for a long time.

Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-From: 381b25d
rpc: keep track of acceptors, and cancel them in StopRPCThreads

Fixes #4156.

The problem is that the boost::asio::io_service destructor
waits for the acceptors to finish (on windows, and boost 1.55).

Fix this by keeping track of the acceptors and cancelling them before
stopping the event loops.

Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-From: cef4494
qt: periodic language update

Pull updated translations from Transifex.

Add mn (Mongolian) language.

Do not update English translation for now as we want to keep
compatibility with 0.9.

Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-From: 795b921
switch from boost int types to <stdint.h>

Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-From: 4b61a6a, 3e74ac2, d56e30c
Github-Pull: #4129