RFC6598 addresses not recognized as private

[gkuenning]

The private? function doesn't recognize the RFC6598 "shared address space", which is basically a new(ish) version of the well known 192.168/16, 172.16/12, and 10./8 spaces. The new space is 100.64.0.0/10.

A complete list of reserved address spaces can be found in the special-purpose address registries at https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml and https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml

I believe that in those two tables, any address marked with "True" in the Source and Destination columns, and "False" in the "Globally Reachable" column, should be considered private. However I'll leave that decision to others.