Make it possible to Crankshaft all kinds of stubs.

Review URL: https://codereview.chromium.org/14307006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14323 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Improve generated code for HDoCompareObjectEqAndBranch on ia32/x64

R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/14083008

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14324 ce2b1a6d-e550-0410-aec6-3dcde31c8c00