MIPS: Add monomorphic CompareNilICs and Crankshaft support

Port r14407 (cae6596b)

BUG=

Review URL: https://codereview.chromium.org/13840006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14427 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Generators can resume

Port r14415 (d358defa) and r14424 (7b549ce7)

Original commit message:
The generator object methods "next", "send", and "throw" now
include some inline assembly to set up a resumed stack frame.  In some
common cases, we can just jump back into the frame to resume it.
Otherwise the resume code calls out to a runtime to fill in the operand
stack, rewind the handlers, and possibly to throw an exception.

BUG=v8:2355
TESTS=mjsunit/harmony/generators-iteration

Review URL: https://codereview.chromium.org/13864010

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14428 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Clean up VMState a little bit.

Port r14421 (31cd7dda)

BUG=

Review URL: https://codereview.chromium.org/14483002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14429 ce2b1a6d-e550-0410-aec6-3dcde31c8c00