Allow explicit configuration of the channel's sortlist, by
specifying a string in the same format as the equivalent
/etc/resolv.conf option.
This allows library users to perform the same configuration
that is available via /etc/resolv.conf, but without needing
to change that file.
Add 3 new functions to set the local binding for the out-going
socket connection, and add ares_set_servers_csv() to set a
list of servers at once as a comma-separated string.
Signed-off-by: Ben Greear <greearb@candelatech.com>