link stage fell over for any program that attempted to use rexec().
Ruserpass() remains undocumented; i could not find any documentation
for it on other systems.
Also added a BUGS section to the man page, stating that this function
constitutes a potential security hole (as well as the underlying
"exec" service).
Submitted by: rgrimes
Originally submitted by: agc@uts.amdahl.com (Alistair G. Crooks)
Obtained from: netbsd-bugs@NetBSD.ORG
