[Misc] Set X Wait Timeout to nil only on GNU systems

As it seems, setting this variable to nil causes an Windows Emacs to busy wait
for input with no time delay between two cycles.  This causes heavy load on the
machine and a non-reacting Emacs.

init.el

@@ -351,8 +351,10 @@
       delete-trailing-lines nil
       x-underline-at-descent-line t
       search-whitespace-regexp "[ \t\r\n]+"
-      visual-line-fringe-indicators '(left-curly-arrow right-curly-arrow)
-      x-wait-for-event-timeout nil)
+      visual-line-fringe-indicators '(left-curly-arrow right-curly-arrow))
+
+(when (memq system-type '(gnu gnu/linux gnu/kfreebsd))
+  (setq x-wait-for-event-timeout nil))
 
 (when on-windows
   ;; treat memory for display time ...  but hey, this is Windows, memory doesn’t