Arm JIT - merge to master

Thought I'd make a pull request myself for a change, mostly for documentation :)

The ARM JIT is a dynamic recompiler from MIPS to ARM. While basic, it delivers a massive speed boost to the MIPS CPU emulation on mobile devices and other ARM-based platforms.

Unfortunately there seem to be some bugs left and it instacrashes on some devices, but on the Android devices where it does work, it's reasonably solid. I think it's time to merge, it can always be further developed in master or in new branches. It's not yet turned on by default in settings so merging should not break things for anyone. 

The diff is a little messy because it contains some external code: the "disarm" arm disassembler by Christoph Giebelink (for debugging) and updated (and then changed) versions of Sonic1's ARM emitter code. Also I renamed the ARM JIT files to avoid colliding with files from the x86 JIT.