sntpd v3.1

Changes

• Slightly improved log messages when failing to resolve DNS names
• Update co-author's last name, changed from Nilsson to Wiberg 2021

Fixes

• Call res_init() when retrying resolving DNS names, this fixes long
  hangs in setup_socket() which sntpd seemingly never recover from.
  This in turn caused it to not respond to SIGTERM properly, while in
  this state (init)
• When either of bind() or connect() fail in setup_socket(),
  return back to main loop() to handle retries, and catch signals