Handle RRSIG signer case consistently

3329.	[bug]	Handle RRSIG signer-name case consistently: We
		generate RRSIG records with the signer-name in
		lower case.  We accept them with any case, but if
		they fail to validate, we try again in lower case.
		[RT #27451]

bin/tests/system/dnssec/ns3/lower.example.db.in

@@ -0,0 +1,26 @@
+; Copyright (C) 2012  Internet Systems Consortium, Inc. ("ISC")
+;
+; Permission to use, copy, modify, and/or distribute this software for any
+; purpose with or without fee is hereby granted, provided that the above
+; copyright notice and this permission notice appear in all copies.
+;
+; THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+; REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+; AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+; INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+; LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+; OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+; PERFORMANCE OF THIS SOFTWARE.
+
+; $Id: lower.example.db.in,v 1.1.2.1 2012/01/17 08:31:00 marka Exp $
+
+$TTL 300	; 5 minutes
+@			IN SOA	MNAME1. . (
+				2012042407 ; serial
+				20         ; refresh (20 seconds)
+				20         ; retry (20 seconds)
+				1814400    ; expire (3 weeks)
+				3600       ; minimum (1 hour)
+				)
+@			NS	NS
+NS			A	10.53.0.3