_{files,dns,yp}_getenetbyaddr() functions from unsigned long to uint32_t.
In rev 1.29, getnetbyaddr(3) was changed to take uint32_t `net' argument
and also passisng uint32_t `net' to nsdispatch(3) varargs, but
these callback functions were not changed accordingly.
Patch was provided by christos, and this fixes amd(8) coredumps on alpha
when /etc/nsswitch.conf has more than one sources for netgroups.