Allow running mjsunit/manual-parallel-recompile on single-core systems.

- Add an %IsParallelSupported() builtin function to  make possible to check support of parallel processing from JavaScripts.
- Change the test script that if parallel recompilation is forced on a single core CPU, expect that it won't be recompiled in parallel.
- Change the  JSFunction::MarkForParallelRecompilation() to fall back gracefully if parallel recompilation is not supported.

BUG=v8:2733
TEST=mjsunit/manual-parallel-recompile

Review URL: https://codereview.chromium.org/17277002
Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15184 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Fix constant function transition. Insert return instruction before returning.

Port r15180 (2f9dcce3)

BUG=

Review URL: https://codereview.chromium.org/17088008

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15185 ce2b1a6d-e550-0410-aec6-3dcde31c8c00