Fixed DOM tests when using libxml2 versions patched against CVE-2014-0191

DOMDocument::substituteEntities needs to be set to true in order for
external entities to be parsed.
Merge branch 'PHP-5.4' into PHP-5.5

* PHP-5.4:
  Fixed DOM tests when using libxml2 versions patched against CVE-2014-0191
Merge branch 'PHP-5.5' into PHP-5.6

* PHP-5.5:
  Fixed DOM tests when using libxml2 versions patched against CVE-2014-0191
Merge branch 'PHP-5.6'

* PHP-5.6:
  Fixed DOM tests when using libxml2 versions patched against CVE-2014-0191