let lambdabot-haskell-plugins depend on lambdabot-trusted

This fix is due to Javier López (see #85).

See also 0fc79d3b87faf1157d934171ea58a07970f37da1.
follow haskell-src-exts-1.16 API changes

- UnGuardedAlt -> UnGuardedRhs
- dropped 3rd field of PatBind
give lambdabot a chance to log in before pinging server

This should fix #87. Note that sending PING commands during connection
registration is not specified in RFC 2812.