Check for task dialog availability even under Vista and later.

Check for task dialog availability even under Vista and later.

Task dialogs are not always available under Vista and later Windows versions
because we might not be using the right (i.e. 6+) version of comctl32.dll.

Improve the check for task dialog availability and fall back to the classic
message box if we can't use it.

Closes #12553.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65816 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775