desktuils/ical: Fix build with Clang 6
- Submitter becomes maintainer
- While here add missing dependencies
http://beefy11.nyi.freebsd.org/data/head-i386-default/p473790_s335878/logs/ical-2.2_4.log
PR: 226799
Reported by: bob@immure.com
Submitted by: fbsd@opal.com