Stop using "Int" for microsecond delays in "base"

[Evan Laforge]

> Maybe, we should stop using Int altogether. Why not use Integer if we
> want integers, and try to implement Integer and its operations more
> efficiently? Int8, Int16, Int32, and Int64 are good when doing system
> programming, CInt is good when interfacing with C, but what is Int good
> for?

It's good for big data structures since it can be unpacked into the
constructor.  I've seen space usage go down by 1/3 after an Integer ->
Int switch.  Integer is a sum type so there's an extra two words of
overhead (if not mistaken, one for the tag, and one for the
indirection since it can't unpack).