Adds a datatypeLibrary-aware datatype resolver to the XML-syntax parser:
the in-scope library is inherited from the nearest ancestor, the default
(empty) library defines only string and token, and the W3C XML Schema
library defines the full built-in set. A type the in-scope library does
not define is an unknown datatype, so the <data>/<value> pattern matches
nothing rather than silently validating.
Adds an nsNameExcept name-class case so nsName with an <except> child
(XML syntax) and prefix:* - name subtraction (compact syntax) narrow a
namespace wildcard. The compact lexer splits prefix:* into a trailing-
colon word plus a star symbol, which the parser now recognizes.
Existing RELAX NG facet tests declared XSD types without the library and
relied on lenient resolution; they now declare the XSD datatypeLibrary,
matching what a conformant processor requires.
A <data type=> pattern now carries a SimpleType (base + facets) rather
than a bare built-in, and its <param name=>value</param> children
populate the facets (minLength, maxLength, length, pattern, min/max
inclusive/exclusive, total/fraction digits), reusing the XSD datatype
facet validation. So a constrained datatype like xsd:string with
minLength rejects too-short values.
datatypeLibrary resolution, typed <value> comparison, and the RNC
datatype parameter blocks remain.
Part of #79
