Turn the NumberToStringStub into a hydrogen stub.

Turn the NumberToStringStub into a hydrogen stub.

This adds a BuildLookupNumberStringCache() in Hydrogen, which will
be used by the hydrogen version of StringAddStub, in addition to the
hydrogen version of NumberToStringStub.

R=mvstanton@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=16874

Review URL: https://codereview.chromium.org/23726041

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16910 ce2b1a6d-e550-0410-aec6-3dcde31c8c00