Enhanced xml parsers

Extends xml parsers with :
- default case
- & and ! prefixes
- tag namespace/name patterns (disjunction of any, constant string, string with opa, trx parser, or parser expression ; with optional binding)
- attribute list patterns, attribute namespace/name/value patterns (like above), & and ! prefixes, as well as ?, +, *, {n}, {n1, n2} suffixes
+ I can write a wiki page for that.
+ somes fixes (see commits messages)