[release] version bump to 13.1 final
Merge pull request #4793 from MartijnKaijser/13.1

13.1
[WinSystemX11GLES] added required SDL header (by SDL_Surface)
reapply koyoing X11-SDL texture fix
[configure] there are arm boards than run XBMC via X11 and SDL
[decoders] Added Linux v4l2 MFC support for ARM Exynos boards. Tested successfully with MFC5 (Exynos4) and MFC6 (Exynos5) on ODROID-U2, ODROID-U3 and ODROID-XU. The codec queries MFC capabilities - MFC6 and above supports NV12, MFC5 supports NV12MT. When MFC5 is found, FIMC converter hardware found in Exynos4 is required. Code was contributed by @owersun, @vamanea and @mihailescu2m.
[mfc] small bugfixes for MFC5
[mfc] fixed formatting acc to XBMC guidelines
[mfc] fixed snprintf string lengths
[mfc] cosmetic fixes
[mfc] fixed some regressions from the previous refactoring