overrun" (http://curl.haxx.se/bug/view.cgi?id=2026240) identifying two
  problems, and providing the fix for them:

  - CURL_READFUNC_PAUSE did in fact not pause the _sending_ of data that it is
    designed for but paused _receiving_ of data!

  - libcurl didn't internally set the read counter to zero when this return
    code was detected, which would potentially lead to junk getting sent to
    the server.