disable MSVC warning 4275 which is harmless and can't be avoided anyhow

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@60943 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/ustring.h

@@ -31,6 +31,12 @@ typedef wxCharTypeBuffer<wxChar32> wxU32CharBuffer;
 typedef wxScopedCharTypeBuffer<wxChar32> wxScopedU32CharBuffer;
 #endif
 
+#ifdef __VISUALC__
+    // "non dll-interface class 'std::basic_string<wxChar32>' used as base
+    // interface for dll-interface class 'wxString'" -- this is OK in our case
+    // (and warning is unavoidable anyhow)
+    #pragma warning(disable:4275)
+#endif
 
 class WXDLLIMPEXP_BASE wxUString: public std::basic_string<wxChar32>
 {
@@ -589,6 +595,10 @@ public:
 
 };
 
+#ifdef __VISUALC__
+    #pragma warning(default:4275)
+#endif
+
 inline wxUString operator+(const wxUString &s1, const wxUString &s2)
     { wxUString ret( s1 ); ret.append( s2 ); return ret; }
 inline wxUString operator+(const wxUString &s1, const char *s2)