Make fractal test work in Webkit and Mozilla using libwebcl

    Reviewed by NO BODY.

    * Created WebCLCommandQueue::enqueueReadImage on libwebcl
    * Added constants:
        CL_PLATFORM_EXTENSIONS
        CL_DEVICE_EXTENSTIONS
Merge pull request #1 from alerock/fractal-studio

Make fractal test work in Webkit and Mozilla using libwebcl