XML parsing completely broken with recent libxml2 library on all oses

[fcavalieri]

Happens in 12.04, 14.04, 15.04, 15.10 Before:

federico@kubuntu-1404:~/zorba/build/bin$ ./zorba -f -q ../../zorba/test/rbkt/Queries/zorba/flwor/flwor24.xq -e file:=file:///home/federico/zorba/zorba/test/rbkt/Queries/zorba/flwor/flwor24.xml
</home/federico/zorba/zorba/test/rbkt/Queries/zorba/flwor/flwor24.xq>:9,24: static warning [zwarn:ZWST0003]: "local:test-sequential": function declared sequential, but has non-sequential body; raised at /home/federico/zorba/zorba/src/compiler/translator/translator.cpp:4545
<?xml version="1.0" encoding="UTF-8"?>

  <a/>
  <c/>
  <b/>

After:

federico@kubuntu-1404:~/zorba/build/bin$ ./zorba -f -q ../../zorba/test/rbkt/Queries/zorba/flwor/flwor24.xq -e file:=file:///home/federico/zorba/zorba/test/rbkt/Queries/zorba/flwor/flwor24.xml
</home/federico/zorba/zorba/test/rbkt/Queries/zorba/flwor/flwor24.xq>:9,24: static warning [zwarn:ZWST0003]: "local:test-sequential": function declared sequential, but has non-sequential body; raised at /home/federico/zorba/zorba/src/compiler/translator/translator.cpp:4545
</home/federico/zorba/zorba/test/rbkt/Queries/zorba/flwor/flwor24.xq>:21,19: dynamic error [err:FODC0006]: invalid content passed to parse-xml:parse(): "closing tag without matching opening tag":file:///home/federico/zorba/build/bin/../../zorba/test/rbkt/Queries/zorba/flwor/flwor24.xq,: loader parsing error; raised at /home/federico/zorba/zorba/src/runtime/parsing_and_serializing/parse_fragment_impl.cpp:262

[fcavalieri]

Regression introduced by CVE-2015-7499-2.patch