Support ARM Linux device and add Beaglebone as a support device

This patch set enables building PPSSPP on an embedded Linux board called the Beaglebone/Beaglebone Black. Minor tweaks are made to easily support thiis board.
Hmm, strange.  Well, we definitely want everything here in RAM for speed reasons, we don't actually want it flushed to a file.  The goal is to have a "backing store" if you will to map physical addresses to.  Ultimately what we're doing here is constructing an area of memory that looks like the PSP's memory so that we don't have to fiddle with the game's pointers.

In PSP-1000 mode, it will need about 35 MB of RAM.  In PSP-2000 mode, about 67 MB.

We do use MAP_ANON, so it might not matter if it's a real file or shm, not sure.

-[Unknown]