VDD discussion result:
- we want to make vcc files rst so that they can be read by rst
  parsers (github) right from the repo
- vcc prototypes should be integrated into the rst
- scn wants to look after this
- we should make the copyright mandatory
- for the time being, we tolerate a missing copyright to make
  existing vmod builds work again, the move to rst will change
  the interface anyway

Closes #1978