nwfilter.rng defines uint16range and uint32range, but in a different
manner (it also allows a variable name as the value, rather than just
a decimal or hex number). I wanted to add uint16range to
basictypes.rng, but my desired definition was parallel to those for
uint8range and uint24range which are defined in basictypes.rng - they
*don't* allow a variable name for the value.

The simplest path to make everyone happy is to make the "plain"
versions in basictypes.rng have simpler names - "uint8", "uint16", and
"uint24". This patch renames uint8range and uint24range to uint8 and
uint24, while the next patch will add uint16.