Simplify output of Times in a specific unit; see Time::As ()
RIPng implementation
[Python bindings] rescan core module
r10652 inadvertently undid part of these earlier commits:

r10646 src/internet/model/ipv4-l3-protocol.cc
r10636 src/dsr/model/dsr-options.cc
r10636 src/internet/model/icmpv6-header.cc
r10636 src/internet/model/ipv4-header.cc