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/pcat/pcat-grep.pl

@@ -0,0 +1,75 @@
+#!/usr/bin/perl
+
+# take a numerical range and ranges and 
+# only show those ranges or not (-v)
+# single numbers: 4
+# ranges: 5-10 (inclusive)
+# separated by comma's
+# -v reverse
+
+use strict;
+
+my %numbers = ();
+my $reverse = 0;
+my $i;
+my $k;
+
+foreach my $r (@ARGV) {
+
+        if ($r eq "-v") {
+                $reverse = 1;
+                next;
+        }
+        
+        if ($r =~ /-/) {
+                my ($s, $e) = split /-/, $r;
+                
+                if ($s > $e) {
+                        next;
+                }
+
+                for ($i = $s; $i <= $e; $i++) {
+                        $numbers{$i} = 1;
+                }
+                next;
+        }
+        $numbers{$r} = 1;
+}
+
+# read in the input, pcat style
+my $line; my $left; my $right;
+$i = 1;
+my $print = 0;
+while(<STDIN>) {
+        if ($i % 4 == 1) {
+                s/^q: //;  # kill it, if we do query diff
+                
+                ($left, $right) = split /:/, $_;
+                foreach $k (keys %numbers) {
+                        if ($k == $left) {
+                                if ($reverse == 1) {
+                                        $print = 0;
+                                } else {
+                                        $print = 1;
+                                }
+                                last;
+                        }
+                        if ($reverse == 1) {
+                                $print = 1;
+                        } else {
+                                $print = 0;
+                        }
+                }
+        }        
+        if ($print == 1) {
+                print $_;
+        }
+        if ($i % 4 == 0) {
+                if ($reverse == 1) {
+                        $print = 1;
+                } else {
+                        $print = 0;
+                }
+        }
+        $i++;
+}