Grammars should be able to check for infinitely recursive constructs

In r128 I had to disable (and remove in r141) the test that verifies that there are no infinitely recursive constructs in the Pyparsing grammar used internally because it took around 1 hour to complete.

This functionality should be back for users to verify this eventually, but it should be part of the API for the grammar (as a wrapper around the .validate() method of the Pyparsing grammar) and this time it shouldn't be included in the Booleano test suite.