MIPS: Minor fixes to simulator and builtins-mips.

MIPS: Minor fixes to simulator and builtins-mips.

Updated to include fixes to several mips arch-specific files, corresponding to recent changes in r7944, r7935, r7926, r7914, r7910, r7895, and parts of r7423, which had previously been missed for mips. Rebased on r7964.

The simulator changes were missed on r7893 for code-stubs-mips,
where the DirectCEntry stuff was added.

There are also a couple small changes to builtins-mips following
r7879 for the other architectures.

BUG=
TEST=

Review URL: http://codereview.chromium.org//7042031

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7977 ce2b1a6d-e550-0410-aec6-3dcde31c8c00