contrib/: add vcal2xapia from Edmond Orignac

cde/contrib/vcal2xapia/README

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+Hello,
+
+I have written a simple AWK program to convert .vcs files into
+XAPIA format files that can then be dragged and dropped on the Calendar
+icon of the front panel to insert an appointment in the CDE calendar.
+
+The program has some limitations. For the moment, it ignores ToDo items
+and only converts appointment items. Also, it has to convert 
+appointments that extend on more than a single day (such as holidays) 
+into daily repeats
+and to transform "UNTIL=" repetitions into a number of repetition.
+This is done by using an average duration of 30.44 days for a month
+and 365.25 days for a year instead of using the correct duration for
+leap years and for months. So the duration of an appointment can
+be sometimes calculated incorrectly.
+
+If you wish to include it with the CDE sources or to post it on the Wiki 
+documentation, I agree to release it under MIT license.
+      http://opensource.org/licenses/MIT
+
+Otherwise, there are better programs in Perl by Adam Stein at:
+http://www.csh.rit.edu/~adam/Progs/programs.html
+but they require to install some extra Perl libraries.
+
+Best wishes,
+
+Edmond Orignac