re PR tree-optimization/81428 (ICE: in build_one_cst, at tree.c:2079 with -O2. Fixed point division.)

	PR tree-optimization/81428
	* match.pd (X / X -> one): Don't optimize _Fract divisions, as 1
	can't be built for those types.

	* gcc.dg/fixed-point/pr81428.c: New test.

From-SVN: r250265