MAXHOSTNAMELEN and the MIN/MAX macros. We now use PATH_MAX and
HOST_NAME_MAX throughout without falling back on MAXPATHLEN or
MAXHOSTNAMELEN and define our own MIN/MAX macros as needed.
Set adminstrative domain for the process when looking up user's
password or group info and when preparing for execve().
Include strings.h even if string.h exists since they may define
different things. Fixes warnings on AIX and others.
