[libunwind][MIPS]: Add support for unwinding in O32 and N64 processes.

This supports the soft-float ABI only and has been tested with both clang
and gcc on FreeBSD.

Reviewed By: sdardis, compnerd

Differential Revision: https://reviews.llvm.org/D38110


git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@320528 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed