whois: bump to version 5.2.17

Fixes serious usability issues (Debian changelog):

  * Fixed whois referrals for .com, .net, .jobs, .bz, .cc and .tv,
    broken by an ICANN-mandated output change:
    https://www.icann.org/resources/pages/rdds-labeling-policy-2017-02-01-en



Use snapshot.debian.org for the .dsc reference, since files tend to
disappear from the official Debian ftp site over time.

Cc: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>