pt.c (maybe_fold_nontype_arg): Use TREE_TYPE of ARG as the criterion to avoid rebuilding expression tree...

	* pt.c (maybe_fold_nontype_arg): Use TREE_TYPE of ARG as the
	criterion to avoid rebuilding expression tree instead of
	processing_template_decl.

	* g++.dg/template/unify1.C: New test.

From-SVN: r44793