Add support to the ARM MC infrastructure to support mcr and friends. This requires supporting

the symbolic immediate names used for these instructions, fixing their pretty-printers, and
adding proper encoding information for them.

With this, we can properly pretty-print and encode assembly like:
	mrc p15, #0, r3, c13, c0, #3

Fixes <rdar://problem/8857858>.

llvm-svn: 123404