This is the first in a series of commits to
implement #17

This reverts commit 9c017c2d12cbc3ee1edfb4e0c1d051882db1bbf6.

Thanks to M. Caubet for pointing this out.

1) Added version guess to avoid warnings

2) At or around l 202 we used to check whether pat
   was of type CircleDot or CirclePlus. I don't
   know why. It gives wrong results when also
   checking for CirclePlus