Allow the nodemap to contain multiple nodes for mibs like IF-MIB

In the IF-MIB, "interfaces" and "ifMIBObjects" both contain
significant subtrees.  Allow nodemap to contain a comma-separated
list of nodes, to handle MIBs like this.
Prepare for FreeBSD 11 and 12.
Merge branch 'V5-5-patches' into V5-6-patches

* V5-5-patches:
  Prepare for FreeBSD 11 and 12.
Merge branch 'V5-4-patches' into V5-5-patches

* V5-4-patches:
  Prepare for FreeBSD 11 and 12.
Merge branch 'V5-6-patches' into V5-7-patches

* V5-6-patches:
  Prepare for FreeBSD 11 and 12.
Merge branch 'V5-7-patches'

* V5-7-patches:
  Prepare for FreeBSD 11 and 12.
Update to current IANA-ADDRESS-FAMILY-NUMBERS-MIB and current RFCs.
Merge branch 'V5-6-patches' into V5-7-patches

* V5-6-patches:
  Update to current IANA-ADDRESS-FAMILY-NUMBERS-MIB and current RFCs.
Merge branch 'V5-7-patches'

* V5-7-patches:
  Update to current IANA-ADDRESS-FAMILY-NUMBERS-MIB and current RFCs.
Use inet_pton onplace of inet_aton to help portability.
Merge branch 'V5-6-patches' into V5-7-patches

* V5-6-patches:
  Use inet_pton onplace of inet_aton to help portability.
Merge branch 'V5-7-patches'

* V5-7-patches:
  Use inet_pton onplace of inet_aton to help portability.
Fix a couple of struct sizes to better match declaration.
Merge branch 'V5-7-patches'

* V5-7-patches:
  Fix a couple of struct sizes to better match declaration.
Prepare for FreeBSD 11 and 12
Prepare for FreeBSD 11 and 12
Merge branch 'V5-5-patches' into V5-6-patches

* V5-5-patches:
  Prepare for FreeBSD 11 and 12
Merge branch 'V5-6-patches' into V5-7-patches

* V5-6-patches:
  Prepare for FreeBSD 11 and 12
Merge branch 'V5-7-patches'

* V5-7-patches:
  Prepare for FreeBSD 11 and 12
Fix bug 2313 for cross compilation.