2013-02-21  Sharath Kamath  <kamath.sharath@gmail.com>

        CreateImage must throw exception on zero height/width.
        Issue #121

        Reviewed by Antonio/Igor.

        When height/width is zero, OpenCL throws Dom exception -65.
        This must be avoided and WebCL must throw a INVALID_MEM_SIZE exception.

        Also createImageWithDescriptor must read the height,width,channelType and
        channelOrder from the WebCLImageDescriptor passed.

        No new tests (OOPS!).

        * Modules/webcl/WebCLContext.cpp:
        (WebCore::WebCLContext::createImage2DBaseImage):
        (WebCore::WebCLContext::createImageWithDescriptor):