re PR c++/17068 (ICE: tree check: expected class 'd', have 'x' (identifier_node) in dependent_template_p, at cp/pt.c:12043)

	PR c++/17068
	* pt.c (dependent_template_p): Treat IDENTIFIER_NODEs as
	dependent.

	PR c++/17068
	* g++.dg/template/operator4.C: New test.

From-SVN: r86199