improve queuing logic of inactive torrents (dont_count_slow_torrents)

git-svn-id: http://libtorrent.googlecode.com/svn/trunk@9968 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda
downloaders only consider download threshold and seeds only consider upload thresholds, for determining whether a torrent is considered inactive or not

git-svn-id: http://libtorrent.googlecode.com/svn/trunk@9969 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda
INT16_MIN and INT16_MAX macros for windows

git-svn-id: http://libtorrent.googlecode.com/svn/trunk@9971 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda