Consolidate patches #1690164, 1683397, and 1690169, all of which refactor…

Consolidate patches #1690164, 1683397, and 1690169, all of which refactor XML-related test suites. The patches are applied together because they use a common output/xmltests file.
Thanks to Jerry Seutter for all three patches.

Lib/test/output/test_pyexpat

-test_pyexpat
-OK.
-OK.
-OK.
-OK.
-OK.
-OK.
-OK.
-OK.
-OK.
-OK.
-OK.
-OK.
-PI:
-	'xml-stylesheet' 'href="stylesheet.css"'
-Comment:
-	' comment data '
-Notation declared: ('notation', None, 'notation.jpeg', None)
-Unparsed entity decl:
-	('unparsed_entity', None, 'entity.file', None, 'notation')
-Start element:
-	'root' {'attr1': 'value1', 'attr2': 'value2\xe1\xbd\x80'}
-NS decl:
-	'myns' 'http://www.python.org/namespace'
-Start element:
-	'http://www.python.org/namespace!subelement' {}
-Character data:
-	'Contents of subelements'
-End element:
-	'http://www.python.org/namespace!subelement'
-End of NS decl:
-	'myns'
-Start element:
-	'sub2' {}
-Start of CDATA section
-Character data:
-	'contents of CDATA section'
-End of CDATA section
-End element:
-	'sub2'
-External entity ref: (None, 'entity.file', None)
-End element:
-	'root'
-PI:
-	u'xml-stylesheet' u'href="stylesheet.css"'
-Comment:
-	u' comment data '
-Notation declared: (u'notation', None, u'notation.jpeg', None)
-Unparsed entity decl:
-	(u'unparsed_entity', None, u'entity.file', None, u'notation')
-Start element:
-	u'root' {u'attr1': u'value1', u'attr2': u'value2\u1f40'}
-NS decl:
-	u'myns' u'http://www.python.org/namespace'
-Start element:
-	u'http://www.python.org/namespace!subelement' {}
-Character data:
-	u'Contents of subelements'
-End element:
-	u'http://www.python.org/namespace!subelement'
-End of NS decl:
-	u'myns'
-Start element:
-	u'sub2' {}
-Start of CDATA section
-Character data:
-	u'contents of CDATA section'
-End of CDATA section
-End element:
-	u'sub2'
-External entity ref: (None, u'entity.file', None)
-End element:
-	u'root'
-PI:
-	u'xml-stylesheet' u'href="stylesheet.css"'
-Comment:
-	u' comment data '
-Notation declared: (u'notation', None, u'notation.jpeg', None)
-Unparsed entity decl:
-	(u'unparsed_entity', None, u'entity.file', None, u'notation')
-Start element:
-	u'root' {u'attr1': u'value1', u'attr2': u'value2\u1f40'}
-NS decl:
-	u'myns' u'http://www.python.org/namespace'
-Start element:
-	u'http://www.python.org/namespace!subelement' {}
-Character data:
-	u'Contents of subelements'
-End element:
-	u'http://www.python.org/namespace!subelement'
-End of NS decl:
-	u'myns'
-Start element:
-	u'sub2' {}
-Start of CDATA section
-Character data:
-	u'contents of CDATA section'
-End of CDATA section
-End element:
-	u'sub2'
-External entity ref: (None, u'entity.file', None)
-End element:
-	u'root'
-
-Testing constructor for proper handling of namespace_separator values:
-Legal values tested o.k.
-Caught expected TypeError:
-ParserCreate() argument 2 must be string or None, not int
-Caught expected ValueError:
-namespace_separator must be at most one character, omitted, or None