INT 2F U - NETWORK REDIRECTOR - RENAME REMOTE FILE
        AX = 1111h
        SS = DS = DOS DS
        SDA first filename pointer = offset of fully-qualified old name
        SDA second filename pointer = offset of fully-qualified new name
        SDA CDS pointer -> current directory structure for drive with file
Return: CF set on error
            AX = DOS error code (see INT 21/AH=59h)
        CF clear if successful
Note:   called by DOS 3.1+ kernel
SeeAlso: INT 21/AH=60h