Highlights:
- Better support for FP compares and branches (BranchF macro)
- Add EmitFPUTruncate() macro, similar to EmitVFPTruncate on Arm.
- Some improvements to long-branch mechanism for mips.
- Add ClampUint8() and ClampDoubleToUint8()

- Minor changes to ic-mips, full-codegen-mips mostly, for improved
code-patching with BinaryOpStub.
- Small changes to stack checking in full-codegen-mips and
regexp-macro-assembler-mips

BUG=
TEST=

Review URL: http://codereview.chromium.org/7888004
Patch from Paul Lind <plind44@gmail.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9307 ce2b1a6d-e550-0410-aec6-3dcde31c8c00