[wmx] [PATCH] wm2: allow user to specify CONFIG_NEW_WINDOW_COMMAND at compile time

Do not set CONFIG_NEW_WINDOW_COMMAND if already defined.
This allows changing it's value using -D without patching the source.

--- a/Config.h
+++ b/Config.h
@@ -7,7 +7,9 @@
 #define CONFIG_NASTY_FONT	  "fixed"
 
 #define CONFIG_EXEC_USING_SHELL   False
+#ifndef CONFIG_NEW_WINDOW_COMMAND
 #define CONFIG_NEW_WINDOW_COMMAND "xterm"
+#endif
 #define CONFIG_EVERYTHING_ON_ROOT_MENU False
 
 // You can't have CLICK_TO_FOCUS without RAISE_ON_FOCUS but the other