GeezerVison

…inidom

Only the structure is checked, not the characters.

A comment ending with '-' was fused with the closing '-->' into '--->'.
A processing instruction was not checked at all: '?>' in the data silently
closed it, and the reserved target 'xml' produced a document which cannot
be parsed.  The identifiers of the document type declaration were
interpolated into single quotes without checks, so an identifier containing
a quote or other illegal character produced XML which is not well-formed,
and a public identifier without a system identifier produced the literal
'None'.