Allow Lua concatenated tables to concatenate functions. This means

that code loading an actor can have an InitCommand even if the actor
itself also has an InitCommand.  The actor's own InitCommand will be
run first, followed by the caller's.

stepmania/Themes/default/Scripts/ActorDef.lua

@@ -17,8 +17,15 @@ local function MergeTables( left, right )
 
 	for key, val in pairs(right) do
 		if ret[key] then
-			Warn( string.format( "%s\n\nOverriding \"%s\"",
-				 debug.traceback(), key) );
+			if type(val) == "function" and
+			   type(ret[key]) == "function" then
+				local f1 = ret[key];
+				local f2 = val
+				val = function(...) f1(...); return f2(...) end
+			else
+				Warn( string.format( "%s\n\nOverriding \"%s\"",
+					 debug.traceback(), key) );
+			end
 		end
 
 		ret[key] = val;