Rename wxMenuItem::MustUseOwnerDrawn() to MSWMustUseOwnerDrawn().

No real changes, just make it clear that this method is MSW-specific and is
about using owner drawn items at MSW level and not wx one.

See #13878.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76201 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/menuitem.cpp

@@ -765,7 +765,7 @@ void wxMenuItem::DoSetBitmap(const wxBitmap& bmp, bool bChecked)
     // support instead of making the item owner-drawn
     SetOwnerDrawn(true);
 
-    if ( MustUseOwnerDrawn() )
+    if ( MSWMustUseOwnerDrawn() )
         return;
 
     // the item can be not attached to any menu yet and SetBitmap() is still
@@ -1326,7 +1326,7 @@ void wxMenuItem::GetColourToUse(wxODStatus stat, wxColour& colText, wxColour& co
     }
 }
 
-bool wxMenuItem::MustUseOwnerDrawn()
+bool wxMenuItem::MSWMustUseOwnerDrawn()
 {
     // MIIM_BITMAP only works under WinME/2000+ so we always use owner
     // drawn item under the previous versions and we also have to use