The POSIX_Poll_Poorly Ada Library

This is the smallest and least transformative library I've ever layered over this POSIX nonsense.  I
separated it from POSIX_TCP_Garbage because my coming TCP library may use poll and other mechanisms,
and this library could be useful by itself, however unlikely.  Poll was selected due to it being the
easiest to model in Ada, with only the ``nfds_t'' type and some text replacement macro names needed.
I strongly considered not using any adjective in this library's name, but suppose it matters little.

Part of the reason for the direct exposure of heavy C language nonsense in this library is its array
nature making type conversions wholly unreasonable; fortunately, careful thought revealed to me long
ago how I may avoid directly exposing anything like this in the greater TCP library, which shall use
Ada's nature to hide the fact that anything like the arrays used by poll are in the programs at all.
.