MIPS: Implement clearing of CompareICs.

MIPS: Implement clearing of CompareICs.

Port r11491 (705d40cc)

Original commit message:
Implement clearing of CompareICs.

This allows CompareICs to be cleared during garbage collection to avoid
cross-context garbage retention through maps stored in CompareIC stubs
for the KNOWN_OBJECTS state.

BUG=
TEST=

Committed: https://code.google.com/p/v8/source/detail?r=11505

[Michael Starzinger, 2012-05-04 07:53:34]

LGTM. Landed.