Merge pull request #4 from twinaphex/master

Libco
add a wrapper for the cpu_thread entry function.
fix cpu_thread_entry type
(PSP) remove #include <pspthreadman.h> ( already included )
add performance counter
make performance logging optional
disable debugging features of the Z80/R800 emulator.
clone Emulator.c in the libretro folder
and update makefile to use it instead
Emulation now executes in the main thread, one frame at a time.
remove some unneeded files and functions
more cleanups
remove framebuffer.c, use image_buffer directly.