If parser runs in debug mode dot files will be generated.

SemanticActionResults instance is now passed in first_pass in the place
of children parameter. This enables dot access operation similar to
parse tree dot navigation.

Comments are now available as a comment list attribute on the parser
object.

Reworked peg_peg example to align with the previous changes.

Rules that consists of just a crossref to another rules were resolving
as a terminal rule down the chain. This fix will make a new rule as
a clone of the last rule down the chain but under a original rule name.

Parsing expressions keep track of the previous parsing expression during
recursive descent. This enables StrMatch to mark terminal for
suppression if called from Sequence.