MIPS: Introduce intrinsic to expose debug state to generated code.

Port r21908 (527abba)

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/343193005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21946 ce2b1a6d-e550-0410-aec6-3dcde31c8c00