Fix bug when setting an out of range date in wxMSW wxDatePickerCtrl.

Fix bug when setting an out of range date in wxMSW wxDatePickerCtrl.

The internally stored date value was getting out of sync with the real date in
the control itself when SetValue() was called with a date out of the currently
set range. This resulted in an assert failure and other unpleasantness later.

Fix the bug and add a unit test checking for it (and also with some other
basic wxDatePickerCtrl checks).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67990 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775