Add RemovePrototype to FunctionTemplate

This allows functions created from a FunctionTemplate to not have a
prototype property, which is required by DOM methods.

R=mstarzinger@chromium.org
BUG=chromium:272440

Review URL: https://codereview.chromium.org/22990003

Patch from Erik Arvidsson <arv@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16341 ce2b1a6d-e550-0410-aec6-3dcde31c8c00