Add a check for GPL licenses with the libtool exception.

third_party/devscripts/licensecheck.pl

 #!/usr/bin/perl -w
 # This script was originally based on the script of the same name from
 # the KDE SDK (by dfaure@kde.org)
 #
 # This version is
 #   Copyright (C) 2007, 2008 Adam D. Barratt
 #
 # 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
@@ skipping 520 matching lines @@
     }
 
     if ($licensetext =~ /under MIT license/) {
         $license = "MIT/X11 (BSD like) $license";
     }
 
     if ($licensetext =~ /As a special exception, you may create a larger work that contains part or all of the Bison parser skeleton and distribute that work under terms of your choice/) {
         $license = $license . "with Bison parser exception";
     }
 
+    if ($licensetext =~ /As a special exception to the GNU General Public License, if you distribute this file as part of a program or library that is built using GNU Libtool, you may include this file under the same distribution terms that you use for the rest of that program/) {
+        $license = $license . "with libtool exception";
+    }
+
     $license = "UNKNOWN" if (!length($license));
 
     return $license;
 }
 
 sub fatal($) {
     my ($pack,$file,$line);
     ($pack,$file,$line) = caller();
     (my $msg = "$progname: fatal error at line $line:\n@_\n") =~ tr/\0//d;
     $msg =~ s/\n\n$/\n/;
     die $msg;
 }