[EXPLORER][COMCTL32] Fix wrong title on taskbar if it has '&' in it (#7073)

The ampersand (&) a.k.a. prefix of
DrawText are specially treated for
adding underscores.
We have to fix drawing on toolbar
button with BTNS_NOPREFIX style.
JIRA issue: CORE-11619

- Delete DT flags hack in taskswnd.cpp.
- Add TOOLBAR_GetButtonDTFlags
  helper function.
- Extend TOOLBAR_DrawString
  parameters for the button info.
- Fix DrawText flags for drawing
  when the button has
  BTNS_NOPREFIX style.

base/shell/explorer/taskswnd.cpp

@@ -287,7 +287,6 @@ public:
 
         // HACK & FIXME: CORE-18016
         HWND toolbar = CToolbar::Create(hWndParent, styles);
-        SetDrawTextFlags(DT_NOPREFIX, DT_NOPREFIX);
         m_hWnd = NULL;
         return SubclassWindow(toolbar);
     }