[Pyparsing] global setDebug feature

[Mike S. <mik...@co...>]

Sometimes it is annoying to try and figure out which elements need a setDebug() to figure out what went wrong.

It would be nice to do:

ParserElement.setDefaultDebug(True)
...
ParserElement.setDefaultDebug(False)

just like you can do:

ParserElement.setDefaultWhitespaceChars()

Then, I could just put this at the top before parser construction, and there isn't anything I would miss (or, at least, nothing in my source).  Pre-built things would still not have debug set, like lineEnd for example; but that's ok.

This more closely matches the feature of yacc/bison debugging, which will spray a ton of detail.  Handy when just turn on all debugging, find and fix the issue, then turn it off.  Easy to do with a one line change in a larger grammar.