don't die on SIGPIPE

this will allow `stint | sed q' to exit with a 0 return status, and also
to wait for the button to be released

TODO

@@ -1,3 +1,2 @@
 * Would it be simpler to rewrite using XCB?
 * Grab Esc to cancel?
-* Handle EPIPE gracefully

stint.c

@@ -17,6 +17,7 @@
  */
 
 #include <stdio.h>
+#include <signal.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 #include <X11/cursorfont.h>
@@ -77,6 +78,10 @@ main(int argc, char *argv[])
 		goto out_ungrab;
 	}
 
+	// Don't die immediately if we get a SIGPIPE
+	struct sigaction sa_ign = { .sa_handler = SIG_IGN };
+	sigaction(SIGPIPE, &sa_ign, NULL);
+
 	// Print colors until Button1 is released
 	while (ev.type != ButtonRelease || ev.xbutton.button != 1) {
 		print_pixel(dpy, root, ev.xbutton.x_root, ev.xbutton.y_root);