[mips] Add support for mips r6, microMIPS r6 and MSA

Verified for all mips archs (mips32, mips32r6. mips64r6).

Patch is a rebased version of:
https://android-review.googlesource.com/153821

Change-Id: I60f576cc44571afd0000ddec4716e1fb0d02d660
54 files changed
tree: 413a9168d9d9c97f7bfffde4d1084b7a6ea71075
  1. build-gdb.sh
  2. build.py
  3. gdb-7.11/