size_t/ssize_t - change to [unsigned] long

size_t/ssize_t - change to [unsigned] long

* change size_t from unsigned int to unsigned long, and change ssize_t
  from int to long for both 32 and 64 bit builds.

  NOTE: This may not last for 32 bit builds, depending on what it breaks
  in pkgsrc land, but the change makes it easier to detect 32/64 bit
  issues with size_t, sizeof, and pointer arithmatic on 32 bit machines.