XML parser accepts text before top-level tag if provided in entity form

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=5965

Reported by Jonas Wallden jonasw@roxen.com

Parser.XML.Simple()->parse(" A ", lambda(mixed ...foo) { werror("%O\n", foo); });
({ /* 5 elements / "error", 0, 0, "All data must be inside tags", ([ / 1 element / "location": 2 ]) }) ({ / 5 elements / "<>", "foo", ([ ]), 0, ([ / 1 element */ "location": 11 ]) })

> Parser.XML.Simple()->parse("  &#65;  <foo/>", lambda(mixed ...foo) { werror("%O\n", foo); });

({ /* 5 elements / "", 0, 0, "A", ([ / 1 element / "location": 9 ]) }) ({ / 5 elements / "<>", "foo", ([ ]), 0, ([ / 1 element */ "location": 15 ]) })

(Haven't checked the XML spec but I doubt it's the intended behavior.)