* tree.c pattern.c: Silenced intel compiler warnings (reported
  by Kjartan Maraas, bug #318517).
* xmlschemas.c: The above changes in pattern.c revealed an
  inconsistency wrt IDCs: we now _only_ pop XPath states, if
  we really pushed them beforehand; this was previously not
  checked for the case when we discover an element node to be
  invalid wrt the content model.
  Fixed segfault in xmlSchemaGetEffectiveValueConstraint().