Warning fixes found under hardest mode of OpenWatcom. Seems clean in Borland, MinGW and DMC.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@29682 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/dialup.cpp

@@ -460,7 +460,7 @@ wxString wxDialUpManagerMSW::GetErrorString(DWORD error)
 
         case 0:
             // we want the error message to start from a lower case letter
-            buffer[0] = wxTolower(buffer[0]);
+            buffer[0] = (wxChar)wxTolower(buffer[0]);
 
             return wxString(buffer);
     }