Submit builtins-mips.cc.

This code submission will compile, but is not testable until the majority
of the mips port is in place. This has been tested externally.

BUG=
TEST=

Review URL: http://codereview.chromium.org//7013031

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7880 ce2b1a6d-e550-0410-aec6-3dcde31c8c00