Bugfix: sort globbed files

Consider something like this in the config file:

    extension jpg
    extension tif

When working with a directory that contains files of both types the
files previously wouldn't get sorted by file name but by extension,
apparently because of how file globbing with a pattern like
`*.{jpg,tif}` works. This commit fixes this, sorting files like
expected.

verso.pl

@@ -549,7 +549,7 @@ sub init_files {
     if (-e $path) {
         $path = normalize_file_path($path);
         (undef, $directory, undef) = fileparse($path);
-        @files = map { decode 'utf8', $_ }
+        @files = sort map { decode 'utf8', $_ }
             grep { ! -d } glob "$directory*.{$ext}";
         if (@files) {
             $index = -d $path ? 0 : first_index($path, @files);