Perl6 rules grammar

[Patrick R. Michaud]

A couple of people have been making contributions to the rx_grammar.pl
file in pugs (modules/Grammars/rx_grammar.pl), so I thought I'd start
maintaining an "official Perl 6 grammar" in the parrot repository,
that can be maintained/monitored closely with PGE.

The latest version of the grammar file is kept at
http://svn.perl.org/parrot/trunk/compilers/pge/P6Rule.grammar, and
is currently a "first draft". It differs somewhat from rx_grammar.pl,
in that it incorporates some of the rule syntax changes that
don't yet appear in S05/A05. (I hope to be bringing S05/A05
more up to date soon, patches are welcome!)

Some constructs needed to fully describe the rules syntax aren't
available in PGE yet; in these cases I've provided a rule as it
should probably look, followed by whatever version of the rule
PGE can currently support.

Also, I know there are some rule syntaxes that are missing in this
first draft, but following "release early/often" I thought I'd
go ahead and publish a somewhat incomplete version for now.
All patches and feedback are greatly appreciated.

Pm