- Scyther binary in www-ccremers hangen voor Sjouke, want daar update
  hij de boel van.
- Maybe add warning for type of matching in the output, maybe stderr.
- SConstruct file should check whether ctags actually exists (avoiding
  errors)
- Proof output should be XML, with an external converter to dot format.
- Internal hash over input files (maybe after parsing?) and switch
  structure. This would make a caching mechanism much easier.