scripts: Handle argument parsing consistently when using Getopt::Long

scripts/changelog/debian.pl

@@ -21,7 +21,7 @@
 use strict;
 use warnings;
 
-use Getopt::Long qw(:config gnu_getopt auto_help);
+use Getopt::Long qw(:config posix_default bundling no_ignorecase);
 use POSIX;
 
 use Dpkg;

scripts/dpkg-mergechangelogs.pl

@@ -24,7 +24,7 @@ use Dpkg::ErrorHandling;
 use Dpkg::Gettext;
 use Dpkg::Version;
 
-use Getopt::Long;
+use Getopt::Long qw(:config posix_default bundling no_ignorecase);
 use Scalar::Util qw(blessed);
 
 textdomain("dpkg-dev");