Tidy up the range normalization code.

Tidy up the range normalization code.

There's a few spots where a range is being altered in-place, but we
fail to call normalize the range.  This patch makes sure we always
call normalize_kind(), and that normalize_kind in turn calls
verify_range to make sure verything is canonical.

gcc/ChangeLog:

	* value-range.cc (frange::set): Do not call verify_range.
	(frange::normalize_kind): Verify range.
	(frange::union_nans): Do not call verify_range.
	(frange::union_): Same.
	(frange::intersect): Same.
	(irange::irange_single_pair_union): Call normalize_kind if
	necessary.
	(irange::union_): Same.
	(irange::intersect): Same.
	(irange::set_range_from_nonzero_bits): Verify range.
	(irange::set_nonzero_bits): Call normalize_kind if necessary.
	(irange::get_nonzero_bits): Tweak comment.
	(irange::intersect_nonzero_bits): Call normalize_kind if
	necessary.
	(irange::union_nonzero_bits): Same.
	* value-range.h (irange::normalize_kind): Verify range.