Log Message:
Update libtorrent to 0.12.6 and rtorrent to 0.8.6.

Changes:
- Added a simple scheduler framework.
- Don't send numwant in STOPPED messages as some trackers are stupid about
  it.
- Reintroduced clearing of epoll event list when a socket is closed as
  it might cause race conditions.
- Added cppUnit test framework. Tests will be added on rather unregular
  basis.
- Logging for SCGI calls.
- Fixed handling of errors when writing out session torrents, it should
  no longer hit an infinite loop.
- Fixed a bug that would cause reading of a piece to hang rtorrent if
  the incoming data contains only data up to a file boundary, but not
  the next file's data.
- Fixes a file handle leak in the execute_capture functions.
- Fixed crash on empty bitfield in 'd.bitfield'.
- Fixed the Object::flag_unordered code to handle initial zero-length
  keys. Ticket #1950.
- Made torrent::Rate::rate_type uint64_t and added sanity checks due to
  reports of bad download/upload values being reported to some trackers.

OK tron@ wiz@