Merge from vendor branch TNF:

Merge from vendor branch TNF:
Add davical.

DAViCal is a server for calendar sharing. It is an implementation of the
CalDAV protocol which is designed for storing calendaring resources (in
iCalendar format) on a remote shared server.

DAViCal supports basic delegation of read/write access among calendar users,
multiple users (or clients) reading and writing the same calendar entries over
time, and scheduling of meetings with free/busy time displayed.

An increasing number of calendar clients support the maintenance of shared
remote calendars through CalDAV, including Evolution, Mulberry, Chandler,
Mozilla Calendar (Sunbird/Lightning), and various other closed-source
products such as Apple's iCal and iPhone.