osx: Add support for zero copy video rendering with VDA
metadata: Split metadata.c into multiple files
backend/image: Fix broken locking around image loader
metadata: Don't use metadata_source_t for temp storage during queries
metadata: Remove locking during I/O

This should make the metadata UI stuff feel a lot more snappy
xmp: Trig end-of-track after first loop

Fixes #2046
Add missing file
Add some ugly hacks for decoding RGBA lossy jpegs

Fixes #1770
Add some more keymappings

Shift-F7: Seek backwards
Shift-F8: Play/Pause
Shift-F9: Seek forwards