strip trailing whitespace to make git commits clean
xsd10: refactor schema element to reduce duplication

Using interleave we can push the check for the targetNamespace down to
be in a group that only affects the import element.  This will simplify
XSD 1.1 support where there is a new composition element (xs:override)
that can precede schemaTop elements.

Note: This change changes the diagnostics from libxml2, which apparently
does not deal with interleave very well.  In this case the new
diagnostics are better.
gitignore: ignore local copies of original xmlschema and relaxng schema
xsd10: refactor wildcard attributes for XSD 1.1

XSD 1.1 will use this as a pattern in its own right.  Also the types of
enumeration values appear to be wrong.
cleanup: remove trailing whitespace in empty element tags

Changes don't use this style; make everything consistent.
cleanup: remove obsolete documentation

My understanding is the original intent of this schema was to attempt to
express the content model of XML Schema Definition within RELAX NG.
Most comments carried information about how XSD worked, and how the
RELAX NG implementation expressed them.

In its current use as purely validation for XSD with RELAX NG-capable
validators, it is more important that there be a clear correlation
between the RELAX NG schema and the normative Schema for Schemas.
Documentation should describe points of difference between the
recognized langauges, not redundantly summarize what XSD is intended to
recognize.
rng4xsd: add
cleanup: tighten correspondence with Schema for Schemas

Massive rework that uses a documented documentation annotation and
preserves a clear mapping between RELAX NG patterns and XSD Schema for
Schema components.  Various inconsistencies were fixed as a
side-effect.  The biggest visible change is elimination of the
type-specific patterns in what used to be simpleRestrictionFacets.
Judgment call: I don't think they were worth the space and inconsistency
with the original schema.
cleanup: correct links
xsd11: clone from xsd10.rng
xsd11: update links, start to distinguish from xsd10
runchecks: support xsd11 schema, clean up output
xsd11: support override
xsd11: implement openContent and defaultOpenContent
xsd11: add new schema attributes
xsd11: add attribute declaration inheritable attribute
xsd11: support targetNamespace on local attributes and elements
xsd11: add anyAttribute notQName
xsd11: add assertions
xsd11: substitutionGroup as list