ntdll: Store the directory identity and search mask in the directory cache

[Piotr Caban]

The patch breaks compilation on mac:
directory.c:1973:42: error: expected identifier
             if (!has_wildcard( dir_data->->mask )) break;
                                          ^
directory.c:2164:34: error: use of undeclared identifier 'dir_data'
     const UNICODE_STRING *mask = dir_data->mask;
                                  ^
directory.c:2216:61: error: use of undeclared identifier 'dir_data'
             union file_directory_info *info = append_entry( dir_data, bu...

Thanks,
Piotr