fix: populate ldns submodule and add autotools to LDNS build stage

- Re-cloned zonemaster-ldns with --recurse-submodules so the bundled
  ldns C library source (including Changelog and configure.ac) is present
- Added autoconf, automake, libtool to Dockerfile.backend ldns-build stage
  so libtoolize + autoreconf can generate ldns/configure during make

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

zonemaster-ldns/ldns/contrib/ldnsx/examples/ldnsx-axfr.py

@@ -0,0 +1,30 @@
+#!/usr/bin/python
+# vim:fileencoding=utf-8
+#
+# AXFR client with IDN (Internationalized Domain Names) support
+#
+
+import ldns
+import encodings.idna
+
+def utf2name(name):
+    return '.'.join([encodings.idna.ToASCII(a) for a in name.split('.')])
+def name2utf(name):
+    return '.'.join([encodings.idna.ToUnicode(a) for a in name.split('.')])
+
+resolver = ldnsx.resolver("zone.nic.cz")
+
+#Print results
+for rr in resolver.AXFR(utf2name(u"háčkyčárky.cz")):
+   # rdf = rr.owner()
+   # if (rdf.get_type() == ldns.LDNS_RDF_TYPE_DNAME):
+   #     print "RDF owner: type=",rr.type(),"data=",name2utf(rr.owner())
+   # else:
+   #     print "RDF owner: type=",rdf.get_type_str(),"data=",str(rdf)
+   # print "   RR type=", rr.get_type_str()," ttl=",rr.ttl()
+   # for rdf in rr.rdfs():
+   #     if (rdf.get_type() == ldns.LDNS_RDF_TYPE_DNAME):
+   #         print "   RDF: type=",rdf.get_type_str(),"data=",name2utf(str(rdf))
+   #     else:
+   #         print "   RDF: type=",rdf.get_type_str(),"data=",str(rdf)
+