SF patch 676472 by Geoff Talvola, reviewed by Ben Laurie.

Geoff writes:
  This is yet another patch to _ssl.c that sets the
  underlying BIO to non-blocking if the socket being
  wrapped is non-blocking. It also correctly loops when
  SSL_connect, SSL_write, or SSL_read indicates that it
  needs to read or write more bytes.

  This seems to fix bug #673797 which was not fixed by my
  previous patch.