PR c/23075
	* c-typeck.c (c_finish_return): Set TREE_NO_WARNING on RETURN_EXPR
	if "return with no value, in function returning non-void" warning
	has been issued.
  	* tree-cfg.c (execute_warn_function_return): Don't look at
	RETURN_EXPRs with TREE_NO_WARNING set.

	* typeck.c (check_return_expr): Add no_warning argument.  Set
	*no_warning to true if "return-statement with no value, in function
	returning" warning has been issued.
	* cp-tree.h (check_return_expr): Adjust prototype.
	* semantics.c (finish_return_stmt): Set TREE_NO_WARNING if
	check_return_expr set *no_warning to true.

	* gcc.dg/pr23075.c: New test.
	* g++.dg/warn/pr23075.C: New test.

From-SVN: r103967