Merge pull request #31 from libretro/master

New PR (libretro)
Merge pull request #32 from libretro/master

Update/build fix Libretro core
[libretro] fixed new input controller & multitap support
[libretro] new RETRO_ENVIRONMENT_SET_GEOMETRY callback is now being used instead of RETRO_ENVIRONMENT_SET_SYSTEM_AV_INFO when screen width/height change
Merge pull request #2 from Monroe88/master

Pull commits from upstream