issue71: fix for mplayer media path length windows problem.

using JNI to make a win32 call to GetShortPathNameW which handles the conversion of a long file name to a short file name.  java side then first converts file name to short version if needed before invoking mplayer executable.
Merge branch '5.5.2' of https://github.com/frostwire/frostwire-desktop into 5.5.2