Make some integer specific ranges generic Value_Range's.

Make some integer specific ranges generic Value_Range's.

There are some irange uses that should be Value_Range, because they
can be either integers or pointers.  This will become a problem when
prange comes live.

gcc/ChangeLog:

	* tree-ssa-loop-split.cc (split_at_bb_p): Make int_range a Value_Range.
	* tree-ssa-strlen.cc (get_range): Same.
	* value-query.cc (range_query::get_tree_range):  Handle both
	integers and pointers.
	* vr-values.cc (simplify_using_ranges::fold_cond_with_ops): Make
	r0 and r1 Value_Range's.