Reviewed by Maciej, Eric.

        - WebCore half of fix for <rdar://problem/4176077> CrashTracer: 6569
        crashes in DashboardClient at com.apple.JavaScriptCore:
        KJS::Bindings::ObjcFallbackObjectImp::type()

        WebCore and JavaScriptCore weren't sharing Instance objects very
        nicely. I made them use RefPtrs, and sent them to bed without dessert.

        * bindings/jni/jni_instance.cpp: Made _instance a RefPtr
        (JavaInstance::~JavaInstance):
        (JObjectWrapper::JObjectWrapper):
        * bindings/jni/jni_instance.h:
        (KJS::Bindings::JObjectWrapper::ref):
        (KJS::Bindings::JObjectWrapper::deref):
        * bindings/jni/jni_runtime.cpp: Made _array a RefPtr
        (JavaArray::~JavaArray):
        (JavaArray::JavaArray):
        * bindings/jni/jni_runtime.h:
        (KJS::Bindings::JavaArray::operator=):
        * bindings/objc/objc_runtime.h:
        - Prohibited copying because that would muss the ref count.
        - Prohibited co...