Don't pass spin text control messages processed at wx level to Windows.

Don't pass spin text control messages processed at wx level to Windows.

Windows messages handled at wx level shouldn't be processed again at Windows
level but we always passed the events forwarded by spin control "buddy" text
window to its default window proc as we had no way to determine whether they
were really handled or not.

Now we do have a way to do, by using the newly added MSWHandleMessage(), so
only pass the messages to default window proc if they hadn't been handled
already.

This notably suppresses the annoying beep which happened if Enter key was
pressed in a wxSpinCtrl with wxTE_PROCESS_ENTER style (as used by the
corresponding wxDataViewCtrl renderer, for example). It probably corrects some
other bugs/discrepancies with the other ports in event handling in wxSpinCtrl
too.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68328 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775