[CVS ci] first attempt to really manage structs

[Leopold Toetsch]

I have started to access struct members.
The init_pmc (and set_pmc) can now have an initializer:
    /* Initialize the struct with some data. This should be an array
     * of triples of
     *   - datatype (enum from datatypes.h)
     *   - count
     *   - offset
     */
Before continuing here (only C<int> access is done yet), I'd like to 
know, if this conecept is ok.

Feedback welcome,
leo