PicoDrive v1.80 (Beta 2)

This is yet another Megadrive / Genesis / Sega CD / Mega CD emulator, which was written having ARM-based handheld devices in mind.

* no 32x/sms yet
* no smooth scrolling in pal/50hz mode (still need add this to kernel/firmware)
* forced vsync because of double buffering, so no way to disable frame limiter (again need to patch kernel)
* occasional sound glitches (also firmware problem)
* no use of hardware scaler yet (needs work)