fold-const.c (associate_trees): Only optimize NEGATE_EXPR in one of the operands into MINUS_EXPR if...

	* fold-const.c (associate_trees): Only optimize NEGATE_EXPR in one
	of the operands into MINUS_EXPR if code is PLUS_EXPR.

	* gcc.c-torture/execute/20020805-1.c: New test.

From-SVN: r56058