(Re-)added Phorward BNF parser
(Re-)added Phorward BNF parser

The pbnf parser is an implementation of the former "GDL" parser that was provided by phorward 0.19 up to 0.21, but with a few modifications regaring the new symbol naming semantics (Terminal and nonterminal - watch the starting letters!).

The parser is yet unfinished in this state and will be extended.

phorward/phorward,phorward/phorward