Improved a bit the time necessary to generate the SDF tables by reducing the size of the grammar.
   - now since I have regex to token declarations, I can test which terminals do I have to reject automatically. The SDF file size halved.
   - giving a proper error message in some rare cases when SDF gives more ambiguities than I was expecting. In the case that I found in the C semantics ==Set is parsed as '__('==(.KList),, Set:K) although I have a follow restriction:  "==" -/- [S].[e].[t]
Merge pull request #507 from kframework/improve-sdf

Improve sdf