Set release version
Merge branch 'master' into release
Set release version RC2
Merge branch 'master' into release
Set release version RC3
Merge branch 'master' into release
Merge branch 'master' into release
Merge branch 'master' into release
Set version RC4
Improve MIB index implementation

Improve how MIBs are indexed, so that we can load
MIB classes when required rather than needing to load
them all upfront.

VarBinds can lookup the MIB entry for a given OID
Rebased from release