[IP] inet_dtop will now always return an IPv4 address if the decimal given is <= 0xffffffff

This has the side affect of never returning "::" as an IPv6 address. This was the only way
I could properly allow IPv4 addresses like "0.0.0.100" (while rare, can actually happen). It's
a lot less likely someone will want an IPv6 address of "::0064" (100).