gdb: pull upstream gdb-7.7 branch to master BUG=None TEST=None Change-Id: Iadd292b96ddc6f217f90667ba7717c90c6e3cf67 Reviewed-on: https://chromium-review.googlesource.com/197053 Reviewed-by: Mike Frysinger <vapier@chromium.org> Commit-Queue: Yunlian Jiang <yunlian@chromium.org> Tested-by: Yunlian Jiang <yunlian@chromium.org>