[MIPS] Add support for R6 compact branch instructions

Changes include:
- Reverting previous unnecessary changes to config.guess and config.sub
  from: 668248dd
- Cherry-picks from GDB and binutils trunks
- Support for R6 compact branch instructions
- Prologue and epilogue detection updates
- MSA support including FP32,FP64 and ‘FP96’
  to support FR0, FR1 and FRE respectively
- Native ptrace updates for new NT_MSA context handling
- Native ptrace updates for obtaining config5 register
- XML support for all MIPS configs in GDB and GDB server

Change-Id: I1886cf6ee6e89229ad11510b90ed698b72eecea8
Signed-off-by: Nikola Veljkovic <Nikola.Veljkovic@imgtec.com>