Update lftp to 4.5.4

Version 4.5.4 - 2014-08-07

new setting mirror:sort-by (name, size, date).
torrent: reduced cpu and memory usage.
fixed occasional "BUG:deadlock" message.
fixed a segfault when a directory contains duplicate file names.
fixed a memory leak in torrent.
fixed byte counters in mirror --depth-first.
fixed timeout checks in FISH.
translations updated (pl).