Fix PR c++/42260

gcc/cp/ChangeLog:
	PR c++/42260
	* cp-tree.h (lookup_conversions): Add new bool parameter to
	declaration.
	* search.c (lookup_conversion): Use new bool parameter in
	definition.
	* call.c (add_builtin_candidates): Don't lookup template conversion
	(convert_class_to_reference, build_user_type_conversion_1,
	 build_op_call): Adjust.
	* cvt.c (build_expr_type_conversion): Likewise

gcc/testsuite/ChangeLog:
	PR c++/42260
	* conversion/cast2.C: New test.

From-SVN: r155415