libstdc++: Fix new tests that fail for ILP32 targets

	* testsuite/20_util/integer_comparisons/equal.cc: Fix invalid
	assumption that long is wider than int.
	* testsuite/20_util/integer_comparisons/greater_equal.cc: Likewise.
	* testsuite/20_util/integer_comparisons/less.cc: Likewise.
	* testsuite/20_util/integer_comparisons/less_equal.cc: Likewise.
	* testsuite/20_util/integer_comparisons/not_equal.cc: Likewise.