Sort interfaces alphabetically
Sort interfaces alphabetically

For Channel.Type.*, Channel.Interface.*, Connection.Interface.*, the
order really doesn't matter, but alphabetical order is easier to scan.

For things like the Call sub-interfaces, the order is significant, so
I left them.

Reviewed-by: Simon McVittie <2b470b34502dbf3ba4bcc04ea7e64f4e0e104f33@collabora.co.uk>

TelepathyIM/telepathy-spec,freedesktop-unofficial-mirror/telepathy__telepathy-spec