Change code to generate ElementIterator because Clang complained.
Moved default arugment to method forward declaration because Clang complained.
(reviewed by faigle, as the previous patched where I forgot to mention him as reviewer)


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@8590 2fb0f335-1f38-0410-981e-8018bf24f1b0