by Jan David Mol)

Revert back mp4 r20330 !

* prefer playlist item's meta title over its name, if available. This work-arounds a rare bug: VLC sometimes tends to show a previous item's name instead of the current one.

* revert the rewrite of MP4_GETSTRINGZ in the previous commit, as strnlen is a GNU-extension and therefore unavailable on Mac OS X and other platforms. I think this way is easier than writing an own implementation for OSX, but feel free to tell me otherwise. (closes #1213)

Fixed a few invalid access on broken files.
Fixed compilation warnings.

Make it automatic.