Update copyright year

Signed-off-by: falkTX <falktx@falktx.com>

LICENSE

@@ -1,5 +1,5 @@
 DISTRHO Plugin Framework (DPF)
-Copyright (C) 2012-2018 Filipe Coelho <falktx@falktx.com>
+Copyright (C) 2012-2021 Filipe Coelho <falktx@falktx.com>
 
 Permission to use, copy, modify, and/or distribute this software for any purpose with
 or without fee is hereby granted, provided that the above copyright notice and this

tests/Demo.cpp

@@ -394,7 +394,7 @@ int main(int argc, char* argv[])
             createAndShowExampleWidgetStandaloneWindow<ExampleTextStandaloneWindow>(app);
 #endif
         else
-            d_stderr2("Invalid demo mode, must be one of: color, rectangles, shapes");
+            d_stderr2("Invalid demo mode, must be one of: color, images, rectangles or shapes");
     }
     else
     {