Method rename

fs/subfs.cpp:148–153

            return underlayfs->link(oldname, newname);
        }
        virtual int rename(const char *oldname, const char *newname) override
        {
            PathCat __(this, oldname);
            PathCat ___(this, newname);
            return underlayfs->rename(oldname, newname);
        }
        virtual int unlink(const char *path) override
        {
            PathCat __(this, path);