Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Add bsnmpd(1)'s SNMP client tools (including SNMPv3 support) to the base system.

Sponsored by: The FreeBSD Foundation (the SNMPv3 bits), Google Summer of Code 2005
Reviewed by: philip@ (mostly), bz@ (earlier version based on p4 ch124545)
Approved by: philip@

Finish repo-copy of lib/libbsnmp/modules to usr.sbin/bsnmpd/modules.
These modules are modules for the daemon, not for the library so
they should be where the daemon is.

Add the build infrastructure for the SNMP daemon that is the base
for the NgATM ILMI daemon and for the tree parsing helper program.