Added wxTimePickerCtrl::GetTime() and SetTime().

Added wxTimePickerCtrl::GetTime() and SetTime().

These methods, taking broken down time representation, avoid the problems
arising due to DST complications when using wxDateTime to represent the time
as special care needs to be taken in this case to avoid using the date part
corresponding to a DST change date at which time is discontinuous.

Document the problem with the old functions and use the new ones in the
sample.

See #14137.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71004 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775