Adding ExtDate library to libkdeedu. ExtDate is a replacement for

Adding ExtDate library to libkdeedu.  ExtDate is a replacement for
QDate that eliminates its arbitrary date-range limits (QDate cannot
accept dates prior to year 1752 or after year 8000).  There is no
theoretical limit to the range of dates that ExtDate can accept, but
I have imposed a range of -50000 to +50000 for now.

The ExtDate library is based on the initial work of Michel Guitel, who
wrote the original ExtDate class.  I have added the following classes:

ExtDateTime (replaces QDateTime)
ExtCalendarSystem (replaces KCalendarSystem)
ExtCalendarSystemGregorian (replaces KCalendarSystemGregorian)
ExtDateTable (replaces KDateTable)
ExtDatePicker (replaces KDatePicker)
ExtDateTimeEdit (replaces QDateTimeEdit)
ExtDateWidget (replaces KDateWidget)

Most of the work was simply pasting in the class to be replaced, and
global-replacing QDate with ExtDate.  However, there are some
remaining issues:

+ currently, only the Gregorian calendar is supported
+ using KLocale to set the date string format does not work
+ API docs are needed

Once the issues have been worked out, I would like to propose to
kde-core-devel that these classes be added to kdelibs for KDE4.
However, I am not sure if any other apps besides KStars really need
very remote dates.

The library includes two test-programs for verifying the performance
of ExtDate.  The first (test_extdate) is a command-line program that
simply outputs the results of 9 tests comparing the performance of
ExtDate and QDate.  If ExtDate is working correctly, then the only
differences will be for dates outside of QDate's valid range.  The
second (test_extdatepicker) is a GUI app showing a KDatePicker and an
ExtDatePicker side-by-side (there is a slight rendering difference
between ExtDatePicker and KDatePicker on my system; I don't know
why this is happening).

The other way to test it is to run kstars; I am going to commit the
ExtDate code in kstars shortly...

CCMAIL: kde-edu@kde.org
CCMAIL: kstars-devel@kde.org
CCMAIL: michel.guitel@free.fr

svn path=/trunk/kdeedu/libkdeedu/; revision=304574