Reviewed by Darin Adler.

        <rdar://problem/5438496> JSGlobalContextCreate crashes when passed a custom class

        * API/JSContextRef.cpp:
        (JSGlobalContextCreate): Specify jsNull() as the prototype and let Interpreter's constructor fix it up to point at builtinObjectPrototype().
        * API/testapi.c:
        (main): Use an instance of a custom class as the global object to ensure the code path is exercised in the test.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@25256 268f45cc-cd09-0410-ab3c-d52691b4dbfc