The registry for IPv4 TOS Byte and IPv6 Traffic Class Octet has been
moved to DSCP registry.

Also uses HTTPS for fetching any IANA resource.

Change-Id: I6a54defc2be4415fac084fcf9dfe0a481d72df33
Reviewed-on: https://go-review.googlesource.com/115220
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>