Fix harmless C4275 MSVC warning in wxMSW DLL builds.

Since the addition of wxMSWOwnerDrawnButton, DLL builds started generated a
lot of warnings about using this non DLL-exported class as base class for the
DLL-exported wxCheckBox and wxRadioButton.

Simply suppress these warnings as they are harmless in this case because the
base class has no static data, which is the real problem this warning hints at.

Closes #16237.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76478 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/checkbox.h

@@ -13,6 +13,13 @@
 
 #include "wx/msw/ownerdrawnbutton.h"
 
+#ifdef __VISUALC__
+    // Disable the warning about non DLL-exported wxMSWOwnerDrawnButton class
+    // used as base for DLL-exported class: it's harmless in this case.
+    #pragma warning(push)
+    #pragma warning(disable:4275)
+#endif
+
 // Checkbox item (single checkbox)
 class WXDLLIMPEXP_CORE wxCheckBox : public wxMSWOwnerDrawnButton<wxCheckBoxBase>
 {
@@ -77,5 +84,8 @@ private:
     DECLARE_DYNAMIC_CLASS_NO_COPY(wxCheckBox)
 };
 
+#ifdef __VISUALC__
+    #pragma warning(pop)
 #endif
-    // _WX_CHECKBOX_H_
+
+#endif // _WX_CHECKBOX_H_