It was a big race condition, please understand how multi-thread works before
touching core files.
 Do not throw away the few first subtitles.

Fixes opening podcasts like http://feeds.feedburner.com/Terravideos

avformat: attachments should still be treated as tracks. this fixes [8c5a9c72]

audiofilters: Do not try to insert user audio-filters when our target is SPDIF. We currently have no way to apply any of our filters to the encoded signal.

Moreover, use a function instead of a macro (like in 0.9-branch)
Partially cherry picked from commit 73ab1cd9

And only fonts so far.

Do not move an already rendered subtitle.

It will allow detecting stupid typos.

configure: Use fno-omit-frame-pointer with --enable-release on Mac OS X, as we are collecting crash log.

Our real demux is incomplete and crashes avcodec. The avformat demux works, so i say we use it until someone fixes this thing.