Port of PPSSPP to the OpenPandora

[ptitSeb]

Yes, Alpha Hack break some game, but make other much faster, at least on the Pandora with its SGX GPU, that's why I putted it in the option screen.
Ok Cores, didn't checked.
Yes, kill is include in signal, but all Rx conflict with other defined Rx in signal, and undef them is not enough (there are not all #define, so cannot be undef)
rt was needed at some point. Didn't check lately if it was the case (for the gettime function IIRC)
I didn't really modifiy Frameskip. I remove the VSync (Pandora specific), and used the Win32 code for FrameSkip. I also modify menu to have 6 FrameSkip choice in stead of 3 (not sure it's a good thing).