Update libretro.h
(OSX) Set min OS version to 10.6
(PSP1) Add PSP1 target
(PSP1) Use EXE_EXT
(OSX PPC) Add PPC rules
Add OSX version minor detection to Makefile
Update libretro.h
Update Makefile
Add Makefile.common
Merge pull request #4 from libretro/master

Libretro updates