Simplify changing window styles in wxMSW code

Add wxMSWWinStyleUpdater and wxMSWWinExStyleUpdater helper classes which
allow writing code changing GWL_STYLE and GWL_EXSTYLE bits,
respectively, in a shorter and more clear way.

There should be no real changes in behaviour.

src/msw/control.cpp

@@ -51,6 +51,7 @@
 #include "wx/msw/uxtheme.h"
 #include "wx/msw/dc.h"          // for wxDCTemp
 #include "wx/msw/ownerdrawnbutton.h"
+#include "wx/msw/private/winstyle.h"
 
 // ----------------------------------------------------------------------------
 // wxWin macros
@@ -421,14 +422,13 @@ bool wxMSWOwnerDrawnButtonBase::MSWIsOwnerDrawn() const
 
 void wxMSWOwnerDrawnButtonBase::MSWMakeOwnerDrawn(bool ownerDrawn)
 {
-    long style = ::GetWindowLong(GetHwndOf(m_win), GWL_STYLE);
+    wxMSWWinStyleUpdater updateStyle(GetHwndOf(m_win));
 
     // note that BS_CHECKBOX & BS_OWNERDRAW != 0 so we can't operate on
     // them as on independent style bits
     if ( ownerDrawn )
     {
-        style &= ~BS_TYPEMASK;
-        style |= BS_OWNERDRAW;
+        updateStyle.TurnOff(BS_TYPEMASK).TurnOn(BS_OWNERDRAW);
 
         m_win->Bind(wxEVT_ENTER_WINDOW,
                     &wxMSWOwnerDrawnButtonBase::OnMouseEnterOrLeave, this);
@@ -448,8 +448,7 @@ void wxMSWOwnerDrawnButtonBase::MSWMakeOwnerDrawn(bool ownerDrawn)
     }
     else // reset to default colour
     {
-        style &= ~BS_OWNERDRAW;
-        style |= MSWGetButtonStyle();
+        updateStyle.TurnOff(BS_OWNERDRAW).TurnOn(MSWGetButtonStyle());
 
         m_win->Unbind(wxEVT_ENTER_WINDOW,
                       &wxMSWOwnerDrawnButtonBase::OnMouseEnterOrLeave, this);
@@ -467,7 +466,7 @@ void wxMSWOwnerDrawnButtonBase::MSWMakeOwnerDrawn(bool ownerDrawn)
                       &wxMSWOwnerDrawnButtonBase::OnFocus, this);
     }
 
-    ::SetWindowLong(GetHwndOf(m_win), GWL_STYLE, style);
+    updateStyle.Apply();
 
     if ( !ownerDrawn )
         MSWOnButtonResetOwnerDrawn();