strange one this: for ages this code
		if(strchr((char *)rp->host, '\n') != nil) {
has been doing a strchr on an rp->host, which is a DN*, not by any means a string.
without the cast, the compiler dutifully warns about it too.
perhaps casting uchar* to char* was force of habit? i've replaced it by rp->host->name,
which at least should be technically correct, but the test itself seems curious to me.

Reference: /n/sources/patch/ndb-remove-cast
Date: Thu Jun 29 12:24:21 CES 2017
Signed-off-by: charles.forsyth@gmail.com

--- /sys/src/cmd/ndb/convM2DNS.c	Thu Jun 29 12:17:56 2017
+++ /sys/src/cmd/ndb/convM2DNS.c	Thu Jun 29 12:17:53 2017
@@ -405,7 +405,7 @@
 		USHORT(rp->pref);
 		dn = NAME(dname);
 		rp->host = dnlookup(dn, Cin, 1);
-		if(strchr((char *)rp->host, '\n') != nil) {
+		if(strchr(rp->host->name, '\n') != nil) {
 			dnslog("newline in mx text for %s", dn);
 			sp->trunc = 1;		/* try again via tcp */
 		}