agent/mibgroup/ip-mib/data_access/defaultrouter_linux: Rework netlink buffer alignment

Based on a patch from Joshua Hoke. See also
https://sourceforge.net/p/net-snmp/bugs/2547/.
Merge branch 'V5-5-patches' into V5-6-patches

* V5-5-patches:
  agent/mibgroup/ip-mib/data_access/defaultrouter_linux: Rework netlink buffer alignment
Fix FreeBSD system define chain
Merge branch 'V5-4-patches' into V5-5-patches

* V5-4-patches:
  Fix FreeBSD system define chain
Merge branch 'V5-5-patches' into V5-6-patches

* V5-5-patches:
  Fix FreeBSD system define chain
Install SNMP-TSM-MIB and SNMP-TLS-TM-MIB
PATCH #a1283: Recognize Oracle ACFS file system (Thanks John Haxby)