Work around a problem of Suns Forte compiler which cant handle the case that an enum...

Work around a problem of Suns Forte compiler which cant handle the case that an enum or a class in a namespace has the same name as the namespace itself, as in
/* ----------------------------------------------- */
/* Problem 10 -- Members with the same name as the */
/* enclosing namespace.                            */
namespace NS3 {
  class NS3 {};
};
NS3::NS3 ns3;

Thus rename the IteratorState enum in the IteratorState namespace into IteratorState_s_.

git-svn-id: https://svn.dealii.org/trunk@5599 0785d39b-7218-0410-832d-ea1e28bc413d