[X86][MIPS][ARM] New machine instruction property 'isMoveReg'

This property is needed in order to follow values movement between
registers. This property is used in TII to implement method that
returns true if simple copy like instruction is recognized, along
with source and destination machine operands.

Patch by Nikola Prica.

Differential Revision: https://reviews.llvm.org/D45204

llvm-svn: 333093