This reverts commit 62b9f5b0.

libvlccore: Rename iso_lang.h to vlc_iso_lang.h because we use VLC_EXPORT there, and plugins may use it.

Remove workarounds for broken (probably very old) FFmpeg .pc files
Errors out if nor swscale headers, nor img_resample() in libavcodec are
present

If stats are too heavy weight to use w/o debug, we should either fix
them or remove them completely anyway

Fix the rawvideo codec when visible_pitch != pitch. (And simplify code) This should fix partial screen captures using non multiple of 16 values.

Add some missing symbols in a blind attempt to fix the buildbots. Feel free to revert if this is wrong.

This is the last fix for libvlc.dylib compilation on Mac OS X.