np.timedelta64 integer coercion in older numpy
Ref #19333 

In sufficiently old numpy (the build that caught this bug was running 1.9.2) timedelta64 comparisons have unexpected behavior:

```
value = np.timedelta64(1, 'ns')
new_value = int(value)
assert value == new_value   # <-- raises with modern numpy, passes with older versions
```

This particular comparison is done in the `RangeIndex` constructor, the result being that sometimes`RangeIndex(value, value*10, value)` returns `RangeIndex(1, 10, 1)` instead of raising.

The immediate problem can be fixed by checking more carefully in the RangeIndex constructor.  No idea if there are other places that are affected.

------
A related behavior that I find unhelpful that is present with 1.14.1 is:

```
>>> td = pd.Timedelta(days=1).to_timedelta64()
>>> pd._libs.lib.is_integer(td)
True
```