Wrap SAX content validation failures as parse errors

[carrerasdarren-cell]

Summary

• wrap IllegalDataException raised while SAX callbacks construct JDOM content in JDOMParseException
• preserve the original cause and partial document, matching the existing SAX error path
• add a regression for an XML 1.1 character accepted by the parser but rejected by JDOM's XML 1.0 verifier

This keeps SAXBuilder.build() failures inside its declared JDOMException contract instead of allowing an unchecked exception to escape.

Fixes #223.

Testing

• Untouched reproducer: XML 1.0 is handled as JDOMParseException; XML 1.1 escapes as IllegalDataException
• Patched reproducer: both inputs are handled as JDOMParseException
• Isolated new JUnit regression: 1 test, 0 failures
• Full Ant suite: 1,904 tests, 0 errors; the new regression passes. The 13 failures are in existing temporary-file URI and StAX output expectations on the modern Java/macOS test environment.