In non-blocking recv functions in libmux and libdraw,

distinguish between "cannot receive without blocking"
and "EOF on connection".

In libmux, do not elect async guys muxers, so that
synchronous RPC calls run in the main event loop
(e.g., in eresized) do not get stuck.

Fixes problem reported by Lu Xuxiao, namely that
jpg etc. would spin at 100% cpu usage.

src/cmd/devdraw/x11-init.c

@@ -47,7 +47,8 @@ static int
 xioerror(XDisplay *d)
 {
 	/*print("X I/O error\n"); */
-	sysfatal("X I/O error\n");
+	exit(0);
+	/*sysfatal("X I/O error\n");*/
 	abort();
 	return -1;
 }