drop support for external ffmpeg
linux: link ffmpeg statically
Merge pull request #4005 from FernetMenta/ffmpeg

linux: link ffmpeg statically
[depends] move ffmpeg to unified deps
[configure] remove internal ffmpeg
remove ffmpeg from tree
ffmpeg: remove dll wrappers
add ffmpeg lock manager
todo: refactor to own file
ffmpeg: move callbacks into separate file
remove ffmpeg dlls from generated headers
not removing win32 as this might still be needed?
sq to configure - add --with-ffmpeg=force option
this will always build our ffmpeg version, even if its found in system
only enable auto building ffmpeg if we are not cross compiling
[rpi] setup-sdk.sh: allow overriding of buildroot and xbmc install paths
also don't require root if not needed
sq to configure - fixup after upstream rebase