Dima Barsky reported a problem with GnuTLS-enabled libcurl in bug report

  #1334338 (http://curl.haxx.se/bug/view.cgi?id=1334338). When reading an SSL
  stream from a server and the server requests a "rehandshake", the current
  code simply returns this as an error. I have no good way to test this, but
  I've added a crude attempt of dealing with this situation slightly better -
  it makes a blocking handshake if this happens. Done like this because fixing
  this the "proper" way (that would handshake asynchronously) will require
  quite some work and I really need a good way to test this to do such a
  change.