Make the X11 interface work again.
Patch ported from https://github.com/tsutsui/mule1.1-netbsd:

commit 9a72fba7d6302e637008dcde1968e51f5f57321b
Author: tsugutomo enami <enami@tsugutomo-enamis-MacBook-Air.local>
Date:   Sat Feb 28 10:46:25 2015 +0900

    Copy O_NONBLOCK bit to old_fcntl_flags so that it won't be lost by unrequest_sigio().

--- emacs-18.59-orig/src/ChangeLog
+++ emacs-18.59/src/ChangeLog
@@ -1,3 +1,8 @@
+2018-07-01  Ulrich Mueller  <ulm@gentoo.org>
+
+	* x11term.c (x_init_1): Save the O_NONBLOCK bit, so that it won't
+	be lost by unrequest_sigio(). Patch from Tsugutomo Enami.
+
 2017-12-07  Ulrich Mueller  <ulm@gentoo.org>
 
 	* s-linux.h (SIGSYS): Don't redefine. Fixes compilation with
--- emacs-18.59-orig/src/x11term.c
+++ emacs-18.59/src/x11term.c
@@ -2105,6 +2105,9 @@
 #ifdef F_SETOWN
 	extern int old_fcntl_owner;
 #endif
+#if defined(F_SETFL) && defined(FASYNC)
+	extern int old_fcntl_flags;
+#endif
 
 	dup2 (ConnectionNumber(XXdisplay), 0);
 #ifndef SYSV_STREAMS
@@ -2131,6 +2134,13 @@
 	fcntl (0, F_SETOWN, getpid ());
 #endif /* F_SETOWN_SOCK_NEG */
 #endif /* F_SETOWN */
+#if defined(F_SETFL) && defined(FASYNC)
+	/*
+	 * Since libxcb sets O_NONBLOCK, copy the bit so that it won't
+	 * dropped by unrequest_sigio().
+	 */
+	old_fcntl_flags = fcntl (0, F_GETFL, 0) & ~FASYNC;
+#endif
 
 	/* Enable interrupt_input because otherwise we cannot asynchronously
 	   detect C-g sent as a keystroke event from the X server.  */