Tested on: Mac OS X 10.4.9

This patch fixes numerous bugs in xml.dom.minidom and expatbuilder.
It fixes all the small-to-middling bugs in minidom's DOM Level 1
compliance that I'm aware of; only large bugs remain (see below).

Changes: These are mainly fixes for bugs found by the W3C DOM Test
Suite for DOM Level 1.  Python 2.5 fails over 120 of these tests; I
got the number down to 48.

  - Exposed expat's XML_GetSpecifiedAttributeCount() as a method of
    pyexpat parser objects.  (This is needed to set Attr.specified
    correctly.)  Documented the new method in Doc/lib/libpyexpat.tex.

  - Attributes that got default values from the DTD didn't show up in
    the DOM.  (This was a violation of the XML 1.0 spec!  See
    http://www.w3.org/TR/REC-xml/#proc-types section 5.1, "Validating
    and Non-Validating Processors".  Even non-validating processors
    must "supply default attribute values" based on a certain subset
    of the DTD!)

  - Attr.specified is now set correctly.  Before, it was always False
    (should have been True).

  - Inserting a node into one of its descendants caused an infinite
    loop!  :-)  Now it throws HierarchyMalarkey, per the spec.

  - Many error conditions specified in the DOM were not detected.  In
    particular, InvalidCharacterErr was never raised.  The new version
    does a lot more checking.

  - Assigning to nodeValue is now a no-op for node types where it's
    defined to be null.

  - Document.createEntityReference() is implemented.  It returns an
    EntityReference node, but the node is not populated from the DTD.
    (That is, the new EntityReference implementation is compliant as
    far as it goes, but incomplete.)

  - Element.removeAttributeNode(attr) now raises NotFoundErr if
    attr belongs to some other Element and merely has the same name as
    an attribute of this Element.

  - Element.setAttributeNode() would sometimes return None erroneously.

  - Element.removeAttributeNode() now returns the removed node.

  - Several CharacterData methods would incorrectly throw if you
    passed node.length as the index.

  - Added Document.xmlVersion (from DOM Level 3).  This affects
    INVALID_CHARACTER_ERR checking as specified.

  - Added tests for all of the above.

  - Removed trailing whitespace from lines in Lib/test/test_minidom.py.

  - Deleted obsolete gc testing from test_minidom.

  - In one or two places, broke very large asserts into many small
    asserts.  (I was debugging something.  This change is inessential,
    but it's a good change, so I kept it.)


DOM Level 1 bugs remaining:

  - A lot of the readonly properties are not implemented as readonly.
    This would be easy to fix with new-style classes, but these are
    old-style classes that are using property() for a few things--I
    haven't tried to understand it yet.  I'm putting this off until
    the present patch lands.

  - All NodeLists should be live views, even the one returned by
    getElementsByName().  It will be hard to fix this while retaining
    pickle backward compatibility, and still harder to do it without
    hurting performance.

  - Attribute nodes' nodeValue and childNodes are supposed to stay in
    sync.  This has all the same problems.

  - EntityReference nodes should be populated with child nodes.  The
    descendants of EntityReference nodes should be readonly.  This is
	slightly less of a headache.


I haven't even tried to run DOMTS level2 tests yet.  I'm sure it'll be
pretty gruesome.