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)