Add plan 9 formats for printing IP, MAC, and other formats.

You can now use things like %I such that
cat /net/iproute
will get you this

10.0.0.0 /128 10.0.0.0 4b   ifc    -
10.0.2.0 ffff:ffff:ffff:ffff:ffff:ffff:a00:200 10.0.2.1 4i   ifc    -
10.0.2.0 /128 10.0.2.0 4b   ifc    -
10.0.2.15 /128 10.0.2.15 4u   ifc    -
10.255.255.255 /128 10.255.255.255 4b   ifc    -
127.0.0.0 /104 127.0.0.0 4i   ifc    -
127.0.0.0 /128 127.0.0.0 4b   ifc    -
127.0.0.1 /128 127.0.0.1 4u   ifc    -
127.255.255.255 /128 127.255.255.255 4b   ifc    -
255.255.255.255 /128 255.255.255.255 4b   ifc    -

Which is quite nice.

Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>