Remove counterproductive lowercasing of GUI ScriptEvent names, refs #127.

a8f48ff7e0 introduced XeroXMB lowercasing of element and attribute names
as a feature.
cf9d8b9797, 4d390f501c, dda6268466 added bugfixes and TODOs because of
that.
f76d0ffdc6, 44fe226dd2 removed the XeroXMB lowercase feature.
This patch removes the lowercasing GUI bugfixes that don't fix any bug
anymore while increasing code complexity and lowering performance
(string copies).

Do not send mouse coordinates objects for events that do not relate to
the mouse.

Store event names in static const members to:
(1) improve performance, ensuring that the CStr is not reconstructed
every call,
(2) obtain compile errors when misspelling event names,
(3) allow reuse of the strings in inherited and friend classes.

Differential Revision: https://code.wildfiregames.com/D2445
Comments by Matei, Philip on 2006-03-11-QuakeNet-#wfg-Meeting-0126.log
and 2006-06-24-QuakeNet-#wfg-Meeting-0139.log

This was SVN commit r23403.

source/ps/Game.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2019 Wildfire Games.
+/* Copyright (C) 2020 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -59,6 +59,8 @@ extern GameLoopState* g_AtlasGameLoop;
  **/
 CGame *g_Game=NULL;
 
+const CStr CGame::EventNameSimulationUpdate = "SimulationUpdate";
+
 /**
  * Constructor
  *
@@ -401,7 +403,7 @@ void CGame::Update(const double deltaRealTime, bool doInterpolate)
 		{
 			{
 				PROFILE3("gui sim update");
-				g_GUI->SendEventToAll("SimulationUpdate");
+				g_GUI->SendEventToAll(EventNameSimulationUpdate);
 			}
 
 			GetView()->GetLOSTexture().MakeDirty();