2014-08-07  Sharath Kamath  <s.kamath@samsung.com>

        Update waitForEvents to support Async calls with UserEvents.

        Fixed #538

        Reviewed by Antonio.

        As per specification, waitForEvents() must take UserEvents when a callback is provided.

        conformance/bindingTesting/eventsAndCallbacks/cl_webcl_waitForEvents.html

        * Modules/webcl/WebCL.cpp:
        (WebCore::validateWebCLEventList):
        (WebCore::WebCL::waitForEvents):