Make JSGlobalContextRetain/Release actually work.

        * API/JSContextRef.cpp:
        (JSGlobalContextRetain):
        (JSGlobalContextRelease):
        Ref/deref global data to give checking for globalData.refCount() some sense.

        * API/tests/testapi.c: (main): Added a test for this bug.

        * kjs/JSGlobalData.cpp:
        (KJS::JSGlobalData::~JSGlobalData):
        While checking for memory leaks, found that JSGlobalData::emptyList has changed to
        a pointer, but it was not destructed, causing a huge leak in run-webkit-tests --threaded.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@35815 268f45cc-cd09-0410-ab3c-d52691b4dbfc