Rewrite checkxrefs in Perl, and add it as test

Create a new version of checkxrefs in Perl, which makes working with
data structures a bit easier than in shell... (and there is no need to
spawn executables all the time)

Also, add it as build time test, so it isn't forgotten anymore.

doc/glossary/CMakeLists.txt

 ########### install files ###############
 kdoctools_create_handbook(index.docbook INSTALL_DESTINATION ${HTML_INSTALL_DIR}/en SUBDIR khelpcenter/glossary)
+
+add_test(NAME glossary-checkxrefs
+    COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/checkxrefs.pl
+    WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+)

doc/glossary/checkxrefs

-#!/bin/sh
-DEFINED_ENTRIES=`sed -ne "s^.*<glossentry id=\"\(.*\)\">.*^\1^p" *.docbook`
-REFERENCED_ENTRIES=`sed -ne "s^.*<glossseealso otherterm=\"\(.*\)\">.*^\1^p" *.docbook | uniq`
-
-# Check for entries which are referenced but not defined.
-for ENTRY in $REFERENCED_ENTRIES; do
-	if ! echo $DEFINED_ENTRIES | grep $ENTRY - > /dev/null 2>&1; then
-		echo "'$ENTRY' referenced but not defined!"
-	fi
-done

doc/glossary/checkxrefs.pl

+#!/usr/bin/env perl
+
+# Copyright (C) 2016 Pino Toscano <pino@kde.org>
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+
+use warnings;
+use strict;
+
+use File::Find;
+
+# Collect the *.docbook files in the current directory.
+my @docbook_files = ();
+sub collect {
+  push @docbook_files, $File::Find::name if $_ =~ /\.docbook$/;
+}
+find(\&collect, '.');
+
+# Collect the list of entries, defined and referenced.
+my %defined_entries;
+my %referenced_entries;
+
+for my $file (@docbook_files) {
+  open(DOCBOOK, "<", $file) || die "$0: can't open $file: $!";
+  while(<DOCBOOK>) {
+    if (/<glossentry id="(.*)">/) {
+      $defined_entries{$1} = 1;
+    } elsif (/<glossseealso otherterm="(.*)">/) {
+      $referenced_entries{$1} = 1;
+    }
+  }
+  close DOCBOOK;
+}
+
+# Check for entries which are referenced but not defined.
+foreach my $entry (keys %referenced_entries) {
+  die "'$entry' referenced by not defined"
+    unless defined($defined_entries{$entry});
+}