Use task dialog for wxProgressDialog implementation in wxMSW.

If available, the task dialog is now used for the wxProgressDialog under
Windows. This provides a much more native looking dialog which doesn't look
out of place under modern Windows versions, unlike the generic implementation.

The internals of the code had to be significantly changed as the task dialog
can only be shown modally so, to emulate wxProgressDialog modeless nature, a
separate thread is used for the progress dialog management.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65352 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -403,13 +403,6 @@ Major new features in this release
 2.9.2:
 ------
 
-MSW:
-
-- Fix Cygwin 1.7 build (David Gangola).
-- Native wxHyperlinkCtrl implementation (Rickard Westerlund, GSoC 2010 project).
-- Allow using wxDC::DrawText() with multiline texts.
-- Fix wxBitmapButton best size determination broken in 2.9.1.
-
 All (GUI):
 
 - Added wxRichMessageDialog (Rickard Westerlund, GSoC 2010 project).
@@ -420,6 +413,15 @@ All (GUI):
 - wxRibbon: added EVT_RIBBONGALLERY_CLICKED event (John Roberts).
 - Add support for CP-866 encoding to wxEncodingConverter (madnut).
 
+MSW:
+
+- Native implementation of wxHyperlinkCtrl and wxProgressDialog under modern
+  Windows versions (Rickard Westerlund, GSoC 2010 project).
+- Fix Cygwin 1.7 build (David Gangola).
+- Allow using wxDC::DrawText() with multiline texts.
+- Fix wxBitmapButton best size determination broken in 2.9.1.
+
+
 
 2.9.1:
 ------