add warning about unreliable clearing of clipboard

src/keepass2android/Resources/values/strings.xml

@@ -64,6 +64,7 @@
 	<string name="brackets">Brackets</string>
   <string name="cancel">Cancel</string>
   <string name="ClearClipboard">Clipboard cleared.</string>
+  <string name="ClearClipboardWarning">Make sure this works on your system and consider using the built-in keyboard if not.</string>
   
   
   

src/keepass2android/services/CopyToClipboardService.cs

@@ -639,7 +639,10 @@ namespace keepass2android
 					Util.CopyToClipboard(_service, "");
 					_handler.Post(() =>
 					{
-						Toast.MakeText(_service, Resource.String.ClearClipboard, ToastLength.Long).Show();
+						Toast.MakeText(_service, 
+							_service.GetString( Resource.String.ClearClipboard) + " " 
+							+ _service.GetString(Resource.String.ClearClipboardWarning), 
+							ToastLength.Long).Show();
 					});
 				}
 			}