Port adapted upstream

[carstene1ns]

Hi, I have partially integrated your vita port upstream: psvita branch.
Nowadays I try to put platform specific things in a separate source file, to not clutter the source too much.
If you have the time, may I ask you to look into it a bit? If all works correctly, it should make your life (and others porting OJ) a bit easier.

[usineur]

I took a quick look, and it looks good to me.
I haven't try to build it with some "dirty" self-made makefile, but if I find time, I will try.