Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Plug an fd leak by using autoh_freeall(3).
Refuse to run unless root.
Check in /etc, /usr/local/etc and ./ for the "autotab" configuration
file.
Add more debug statements.

sync with private code:

fix a 5.x'ism that 4.x needs protection from.
make this code compile standalone.

Enter the autofs.