It is available platforms that have SSE 4.1 and allows us to handle
negative numbers without deoptimization. Before we would deoptimize
on negative inputs to Math.floor. x64 already uses this instruction.

* Change Math.floor unit test to make sure every test case gets
optimized by changing the source code for each test case.

* Fix HIR debug printing for some instructions.
Review URL: http://codereview.chromium.org/7628017

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8921 ce2b1a6d-e550-0410-aec6-3dcde31c8c00