tftpd option handling is not RFC-compliant. This causes picky clients (such as curl) to fail transfers.

Reference: /n/sources/patch/applied/tftpd-rfc
Date: Fri Sep  7 17:56:53 CES 2012
Signed-off-by: sstallion@gmail.com

--- /sys/src/cmd/ip/tftpd.c	Fri Sep  7 17:56:00 2012
+++ /sys/src/cmd/ip/tftpd.c	Fri Sep  7 17:55:57 2012
@@ -342,9 +342,6 @@
 
 	if (bp + 3 >= ep)
 		return -1;
-	*bp++ = '\0';
-	*bp++ = '\0';			/* overkill */
-	*bp++ = '\0';
 
 	if (write(fd, buf, bp - buf) < bp - buf) {
 		syslog(dbg, flog, "tftpd network write error on oack to %s: %r",