Added shortcut to clear chat

F12 will now clear the chat in the main chat.

cockatrice/src/tab_room.cpp

@@ -54,6 +54,7 @@ TabRoom::TabRoom(TabSupervisor *_tabSupervisor, AbstractClient *_client, ServerI
     QMenu *chatSettingsMenu = new QMenu(this);
 
     aClearChat = chatSettingsMenu->addAction(QString());
+    aClearChat->setShortcut(tr("F12"));
     connect(aClearChat, SIGNAL(triggered()), this, SLOT(actClearChat()));
 
     chatSettingsMenu->addSeparator();