MFC r311741,r311761:

r311741:

Add a REVISION section to track changes for the hostres module

There haven't been any changes to the MIB definition, so the REVISION remains
static at the version it was imported at

r311761:

Add a REVISION section to track changes for the BEGEMOT-NETGRAPH MIB file

This change also documents the modification harti made to a handful of
objects in r122758 (the max OCTET STRING width was increased from 15 to
31 octets)

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

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

Replace all uses of the old netgraph constants NG_*LEN by the new
constants NG_*SIZ that include the trailing NUL byte. This change
is mostly mechanical except for the replacement of a couple of snprintf()
and sprintf() calls with strlcpy.

Add build infrastructure for libbsnmp and the modules. Add the
netgraph module for the SNMP daemon.