Make mips-specifc changes for r7999, r8001, r8002.

Also bring in changes for older commits 7203, 7279, 7693, 7715, 7788.

Mips changes for 7715 (Arm: Support hardfloat in SCons build), and
7693 (Implement hardfloat calling convention in macro assembler and simulator)
resulted in changes to SConstruct.

BUG=
TEST=

Review URL: http://codereview.chromium.org//6966031

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8022 ce2b1a6d-e550-0410-aec6-3dcde31c8c00