MIPS: Add signal context definitions for use with Android.
MIPS: Add signal context definitions for use with Android.

As with Arm, the kernel defines this stuff, but bionic lib does not.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/9298003
Patch from Paul Lind <plind44@gmail.com>.

git-svn-id: b158db1e4b4ab85d4c9e510fdef4b1e8c614b15b@10525 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh