Merge pull request #2 from twinaphex/master

Trivial changes
add Makefile.mini to linux-sdl
emulation now works but blocks in the CPU thread
implement basic context switching using "ucontext.h".
video/audio now work, timing still wrong.
fix timing
small workaround for the timing problem, will need a proper
implementation later.
add msx2 extension to system info
default machine type to MSX2+
move cpu_thread stack allocation to retro_init
small cleanups
use RGB565 instead of RGB1555
update makefile
remove unused defines
remove the -DNO_ASM flag for x86/x86_64 architectures
(PSP) fix build