middle-end/113396 - int128 array index and value-ranges

middle-end/113396 - int128 array index and value-ranges

The following fixes bogus truncation of a value-range for an int128
array index when computing the maximum extent for a variable array
reference.  Instead of possibly slowing things down by using
widest_int the following makes sure the range bounds fit within
the constraints offset_int were designed for.

	PR middle-end/113396
	* tree-dfa.cc (get_ref_base_and_extent): Use index range
	bounds only if they fit within the address-range constraints
	of offset_int.

	* gcc.dg/torture/pr113396.c: New testcase.