Fixed linkage for Is template.

With static linkage, clang 3.3 is unhappy about unused functions

   template <> inline bool Is<JSFunction>(Object* obj)
   template <> inline bool Is<JSArray>(Object* obj)

in any compilation unit apart from acessors.cc.

R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/14836014

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14657 ce2b1a6d-e550-0410-aec6-3dcde31c8c00