Use nearlabel AFAP in lithium codegen

BUG=
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/47533002

Patch from Weiliang Lin <weiliang.lin@intel.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17583 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Removed dead function V8::FillHeapNumberWithRandom.

Removed a useless test case along the way.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/65143007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17584 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Use register allocator for context on x64.

BUG=
R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/50863002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17585 ce2b1a6d-e550-0410-aec6-3dcde31c8c00