These share their locale data with the Gregorian calendar, making them
virtually free to add. Still leave them out of the boot-strap build,
though.
[ChangeLog][QtCore][QCalendar] Added support for Julian and Milankovic
calendars. These are enabled by default, except in bootstrap builds.
Change-Id: I585045ed9e78c1e959957f6772b3e144093b701c
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>