Remove global 'temp' variable from titlerender.cpp

Just a miscellaneous code cleanup.

There's no glitches that take advantage of the previous situation,
namely that 'temp' was a global variable in Logic.cpp and editor.cpp.
Even if there were, it seems like it would easily lead to some undefined
behavior. So it's good to clean this up.

desktop_version/src/titlerender.h

@@ -8,8 +8,6 @@
 #include "Map.h"
 #include "Script.h"
 
-extern int temp;
-
 void titlerender();
 
 void towerrender();