macosx_events: fix modifiers handling with media keys

This was caused by a typo. Regression from add7c2955df.

Fixes #213
mpvcore/input: Fix build without pthreads
mplayer: try to resume playback only if a resume file actually exists

Well, this was dumb. The resume message was printed for every file,
whether a resume config file existed or not.
etc: delete mplayer.xpm

I don't think we need this anymore.
Merge branch 'master' into lua_experiment