from sources/david

Fixes the problem with orphan fromnet() procs accumulating if their 
respective fromstin() were hung up (read(0) < 0). 

The SSH servers we have around (OpenSSH of many different versions) do 
not cause hang up when they see SSH_CMSG_EOF alone. 

Reference: /n/atom/patch/applied/ssh1-hangup
Date: Sat Mar 22 18:00:38 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/ssh1/ssh1.c	Sat Mar 22 18:00:27 2014
+++ /sys/src/cmd/ssh1/ssh1.c	Sat Mar 22 18:00:28 2014
@@ -562,7 +562,8 @@
 		sendwritemsg(c, buf, n);
 	}
 	sendwritemsg(c, "", 0);
-	atexitdont(atexitkiller);
+	if(n >= 0)				/* weren't hung up upon? */
+		atexitdont(atexitkiller);
 	exits(nil);
 }