[ANNOUNCE] Libical 3.0.13

[Allen Winter]

Announcing Libical 3.0.13.  This is the 13th bugfix release for Libical 3.0
This release is binary and source compatible with version 3.0.0.

Highlights of this Release:
----------------------------------- 
 *  icalcomponent_get_dtend() return icaltime_null_time(), unless called on VEVENT, VAVAILABILITY or VFREEBUSY
 *  icalcomponent_get_duration() for VTODO calculate with DUE instead of DTEND
 * Replace CMake FindBDB with FindBerleyDB (https://github.com/sum01/FindBerkeleyDB)
 * Fix finding ICU and BerkeleyDB on Mac (look for homebrew installs first)

The source code can be found on GitHub at: https://github.com/libical/libical

Tarballs and zipballs for v3.0.13 are available from: https://github.com/libical/libical/releases

"Libical is an Open Source implementation of the iCalendar protocols and protocol data units.
The iCalendar specification describes how calendar clients can communicate with calendar
servers so users can store their calendar data and arrange meetings with other users."

Libical implements:
* RFC5545, RFC5546, RFC7529
 * the CalDav scheduling extensions in RFC6638
 * iCalendar extensions in RFC7986
 * plus the iCalendar iMIP protocol in RFC6047.

 For more information about Libical, please visit http://libical.github.io/libical/