ENHANCED: CLP(FD): Faster in/2 for integer in ground L..U range.
                   Ulrich Neumerkel.

 Example, previously:

   %?- N=500000, time((between(1,N,_), 3 in 1..10,false)).
   %@ % 17,000,001 inferences, 2.423 CPU in 2.436 seconds (99% CPU, 7014808 Lips)
   %@ false.

 Now:

   %?- N=500000, time((between(1,N,_), 3 in 1..10,false)).
   %@ % 1,000,003 inferences, 0.165 CPU in 0.170 seconds (97% CPU, 6076534 Lips)
   %@ false.