* gnulib-tool: Use --local-dir to construct compound
$local_gnulib_path path instead of $local_gnulib_dir. Determine
PATH_SEPARATOR early.
(local_gnulib_dir): Rename into $local_gnulib_path everywhere.
(func_gnulib_dir): Cut out PATH_SEPARATOR detection code into
func_determine_path_separator because that needs to be detected
earlier now.
(func_determine_path_separator): New function.
(func_path_foreach, func_path_foreach_inner): New functions.
(func_path_prepend, func_path_append): Likewise.
(func_lookup_local_file, func_lookup_local_file_cb): Likewise.
(func_lookup_file, func_all_modules): Use new functions to work
with local_gnulib_path.
(func_modules_in_dir, func_exists_module): New callbacks for
func_path_foreach.
(func_exists_module, func_get_tests_module): Likewise.
(func_is_local_file, func_should_symlink): New helper methods.
(func_add_file, func_update_file): Use new func_should_symlink
instead, DRY.
(func_reconstruct_cached_local_gnulib_path): New helper.
(func_reconstruct_cached_dir): New callback.
(func_import): The cached_local_gnulib_dir renamed to
cached_local_gnulib_path similarly to local_gnulib_dir.
Use new func_reconstruct_cached_local_gnulib_path.
(func_count_relative_local_gnulib_path): New sub-method.
(func_create_testdir): Use func_should_symlink, DRY.
(func_create_megatestdir): Use new functions to work with
local_gnulib_path correctly.
(func_append_local_dir): New helper.