MIPS: Handle constants in new space by making macro-assembler smarter.

Port r17376 (9af4f51)

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/57873004

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17463 ce2b1a6d-e550-0410-aec6-3dcde31c8c00