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.

From-SVN: r102805