Update to "simplified" RFC 2822 grammar

I have made some fairly minor changes to the "simplified"
RFC 2822 grammar at
http://users.erols.com/blilly/mparse/rfc2822grammar_simplified.txt

1. added some lines/characters to support parsing/formatting
   by an ABNF formatter (http://users.erols.com/formatting/abnff)

2. the formatter found a few errors (3 or 4 extraneous right
   parentheses, and an obs-comments alternative incorrectly
   labelled comments; these have been fixed