This fixes quoted strings, like <tag>"Hello \"World\""</tag>,
which otherwise might not be processed correctly because
the XML_CharacterDataHandler isn't guaranteed to be called
exactly once per element. It certainly isn't when a string
contains entities, ie: <tag>"'Hello \"World\"'"</tag>
certainly fails to be unescaped with the old code.
Moreover, the old unescape code things that a singly quote
is actually a quoted string (not noting that begin and end
quote are the same) and destructs all " entities; also
fixed with this commit.
d549e549d8