My apologies for the many changes at once, but quite a few were needed to enable tunneling.
I'll commit patches in small increments from now on.
In respons to your questions:
   * Can the GOmxPadData be included in the GOmxPort?

-> It can, depending on how you see the GOmxPort: does it contains all data related to a GstPad, or does it contain all data of to the OMX Port that is related to a GstPad?

     * The GOMX-Core-Pointer should be a function call instead, perhaps
       even an interface, check GstXOverlay[1]
-> I'm sorry, I'm not so familiar with all of the gst functions yet, but how would you export this function pointer to another gstelement?