[MIPS] ORC JIT support

This patch adds support for ORC JIT for mips/mips64 architecture.
In common code $static is changed to __ORCstatic because on MIPS
architecture "$" is a reserved character.

Patch by Luka Ercegovcevic

Differential Revision: https://reviews.llvm.org/D49665

llvm-svn: 341934