Fix appearance of wxMSW wxToggleButtons with bitmaps in pressed state.

Correct the "pushed" state determination in our own drawn code, it didn't work
for wxToggleButton which doesn't return BST_PUSHED from BM_GETSTATE. But it
does have BM_GETCHECK returning its state directly, so add a new virtual
MSWIsPushed() method and implement it differently for it.

Closes #13755.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78251 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/anybutton.h

@@ -73,6 +73,8 @@ protected:
     void MakeOwnerDrawn();
     bool IsOwnerDrawn() const;
 
+    virtual bool MSWIsPushed() const;
+
 private:
     wxDECLARE_NO_COPY_CLASS(wxAnyButton);
 };