deskutils/calendar-data: convert all files to UTF-8

The different calendars have traditionally been provided in locale
specific 8-bit encodings.

With this update they are all provided in UTF-8 encoding, which will
be automatically converted to the encoding selected in the process
environment of the calendar program.

On systems with ICONV support compiled into the calendar program, the
output will be identical to that generated before. All calendar files
have been checked by translating them back to their original encoding
and comparing them with the previous version.

The main advantage of having these files in UTF-8 is ease of editing,
since it is no longer encessary to have the editor configured for the
particular encoding of each file.

On UTF-8 consoles, ICONV support is no longer required to display
calendars with foreign encodings.

Pull Request: https://github.com/freebsd/calendar-data/pull/1