Fix some misc bugs in libcmyth:

    - Change cmyth_rcv_okay() and add cmyth_rcv_match() since the "OK"
      responses can be in either upper or lower case.
    - Fix cmyth_conn_connect_pathname() to error out if a connection
      handle is not provided.
    - Ensure that calls to select() and recv() are retried if interrupted
      by a signal.
Ensure libcmyth is built against the local version of librefmem.