Added support for RetroPlayer builds

To compile:
$ PROJECT=Generic ARCH=i386 XBMC=retroplayer make release

Conflicting patches (removed from retroplayer project):
* xbmc-995.01-xvba_support-4083650.patch

Added patches
* xbmc-0001-Replace-x64-repo-with-32-bit-repo.patch.i386
* xbmc-990.26-PR3210.patch (cherry-picked from ac359292c5c45353b2e4633cc6e07c9a29f48dbf)
Fix XBMC compile error: use internal FFmpeg

PR:2878 (https://github.com/xbmc/xbmc/pull/2878) replaced deprecated CodecID with AVCodecID, but apparently OpenELEC's FFmpeg doesn't provide AVCodecID so disable OpenELEC's FFmpeg and use XBMC's internal FFmpeg.