CREDITS: Added Max Horn to GUI credits

The GUI system was originally written completely by me, as is easily
verifiable by inspecting the commit logs of the gui subdirectory, or e.g.
specific files like gui/widget.cpp.

1 files changed, 1 insertions, 0 deletions

diff --git a/AUTHORS b/AUTHORS
index a0326c015f..251ec615b6 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -418,6 +418,7 @@ ScummVM Team
        Johannes Schickel            - (retired)
 
     GUI:
+       Max Horn                     - (retired)
        Vicent Marti
        Eugene Sandulenko
        Johannes Schickel            - (retired)