pt.c (determine_specialization): Just return an error_mark_node.

pt.c (determine_specialization): Just return an error_mark_node.

	* pt.c (determine_specialization): Just return an error_mark_node.
	Also print the decl we want in error messages.  If we complain,
	return error_mark_node.
	(tsubst_friend_function): Set lineno and input_filename so
	error messages will be useful.
	(instantiate_template): Just return an error_mark_node.
	* pt.c (print_template_context): Add new argument.
	(maybe_print_template_context): New fn.
	(push_tinst_level): Increment tinst_level_tick.
	(pop_tinst_level): Likewise.
	* errfn.c (cp_thing): Call maybe_print_template_context.  Use
	xrealloc instead of xmalloc.
	* typeck.c (build_unary_op, CONVERT_EXPR): Propagate TREE_CONSTANT.

From-SVN: r19946