problem with it (SIGSEGV-style). It clearly showed that the existing
  socket-state and state-difference function wasn't good enough so I rewrote
  it and could then re-run Jeff's program without any crash. The previous
  version clearly could miss to tell the application when a handle changed
  from using one socket to using another.

  While I was at it (as I could use this as a means to track this problem
  down), I've now added a 'magic' number to the easy handle struct that is
  inited at curl_easy_init() time and cleared at curl_easy_cleanup() time that
  we can use internally to detect that an easy handle seems to be fine, or at
  least not closed or freed (freeing in debug builds fill the area with 0x13
  bytes but in normal builds we can of course not assume any particular data
  in the freed areas).

"dump" a hash table which is useful when tracking problems with data stored
in one of our hashes.

don't expect fully qualified names we need to cut them off at the first dot.

of them can be completetly removed though...

cache within the multi handle.

for easier future error-tracking.

  while not fixing things very nicely, it does make the SOCKS5 proxy
  connection slightly better as it now acknowledges the timeout for connection
  and it no longer segfaults in the case when SOCKS requires authentication
  and you did not specify username:password.

" !defined(__GNUC__) || defined(__MINGW32__)" implies
CygWin.

name resolves. It could get stuck in the wrong state.

allow applications to set their own socket options.

properly if you removed a "live" handle from a multi handle with
curl_multi_remove_handle().

code when doing pure ipv6 EPRT connections.

command on subsequent requests on a re-used connection unless it has to.