fold-const.c (extract_muldiv): Check whether c divides op1 exactly if operation is not multiplication.

2000-07-08  Toon Moene  <toon@moene.indiv.nluug.nl>

	* fold-const.c (extract_muldiv) case PLUS_EXPR, MINUS_EXPR:
	Check whether c divides op1 exactly if operation is not
	multiplication.

From-SVN: r34928