Handle all kind of arguments in the ToBooleanStub. While this is not very thrilling in itself, it is one of several steps to add type recording to this stub. Removed a duplicate check for null in the ARM stub and made a tiny simplification, removing a sub instruction.

As a side note, this change has some positive impact on the performace, e.g. imaging-darkroom is 8.3% faster and ws-ieee754conv is even 19.9% faster. No idea why the speedup is so big in some cases, but never look a gift horse in the mouth... ;-)
Review URL: http://codereview.chromium.org/7042004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7926 ce2b1a6d-e550-0410-aec6-3dcde31c8c00