Demystified floating point ABI function names.

This unifies the names used for floating point ABI abstraction across
ARM and MIPS and makes them more comprehensible. Note that in the
underlying implementation, ARM doesn't care about the argument/result
distinction, while MIPS does, but we want to abstract from that, too.

Nuked an unused related function on the way.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/136613003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18567 ce2b1a6d-e550-0410-aec6-3dcde31c8c00