Calling XSetInputFocus() with non-"stale" time.
I believe a change in Xorg facilitated this bug where, occasionally,
a FocusOut event would immediately follow a FocusIn event, leaving
focus reverted to Root window.
References:
	https://bugs.freedesktop.org/show_bug.cgi?id=83900
	http://marc.info/?l=openbsd-misc&m=141067888307365&w=2

--- src/Window.cc.orig	Tue Oct 18 10:01:41 2005
+++ src/Window.cc	Tue Apr 25 16:42:41 2017
@@ -43,6 +43,7 @@
 #endif
 
 #include <assert.h>
+#include <stdlib.h>
 
 /*
   sometimes C++ is a pain in the ass... it gives us stuff like the
@@ -2194,7 +2195,7 @@ bool BlackboxWindow::setInputFocus(void) {
   }
 
   XSetInputFocus(blackbox->XDisplay(), client.window,
-                 RevertToPointerRoot, blackbox->XTime());
+                 RevertToPointerRoot, CurrentTime);
 
   if (client.wmprotocols.wm_take_focus) {
     XEvent ce;