PR c/23113

	PR c/23113
	* stmt.c (warn_if_unused_value): Check TREE_NO_WARNING at start.
	Don't handle NOP_EXPR, CONVERT_EXPR and NON_LVALUE_EXPR
	specially.  Check for side effects only for COND_EXPR.
	* c-typeck.c (c_finish_stmt_expr): Mark statement expression
	return with TREE_NO_WARNING.

testsuite:
	* gcc.dg/Wunused-value-1.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@102805 138bc75d-0d04-0410-961f-82ee72b054a4