twisted u_name and m_name

Fix Bug#523.

Additional Info:
The following line in ofork.c may also be wrong.

    /* Somone has used write_fork, we assume file was changed, register it to file change event api */
    if (ofork->of_flags & AFPFORK_MODIFIED) {
        struct dir *dir =  dirlookup(ofork->of_vol, ofork->of_did);
        bstring forkpath = bformat("%s/%s", bdata(dir->d_fullpath), of_name(ofork));
        fce_register(FCE_FILE_MODIFY, bdata(forkpath), NULL, fce_file);
        bdestroy(forkpath);
    }