Merge pull request #2 from aliaspider/master

initial port of gpsp to libretro.
Remove zip.c/zip.h
Remove gui.c
Remove useless GUI font code
Remove non-libretro code in input.c
Remove non-libretro code in sound.c
Silence warning in libco/x86.c
Assume PC_BUILD
Get rid of non-libretro/SDL code in video.c
Remove unused screen_filter2
Remove set_clock_speed
Remove unused clock_speed variable
Simplify render_audio
Simplify sound_timer function
Simplify gbc_sound_wave_update
Get rid of gbc_sound_load_wave_ram macro
De-macroize render_sample macros
Clean up some unused stuff
Move IN_MEMORY_C ifdefs to memory.c
Cleanups - main.c