Roland Blom filed bug report #1481217

(http://curl.haxx.se/bug/view.cgi?id=1481217), with follow-ups by Michele Bini
and David Byron. libcurl previously wrongly used GetLastError() on windows to
get error details after socket-related function calls, when it really should
use WSAGetLastError() instead.

When changing to this, the former function Curl_ourerrno() is now instead
called Curl_sockerrno() as it is necessary to only use it to get errno from
socket-related functions as otherwise it won't work as intended on Windows.

lib/sendf.c

@@ -335,7 +335,7 @@ CURLcode Curl_write(struct connectdata *conn,
       bytes_written = (ssize_t)swrite(sockfd, mem, len);
 
     if(-1 == bytes_written) {
-      int err = Curl_ourerrno();
+      int err = Curl_sockerrno();
 
       if(
 #ifdef WSAEWOULDBLOCK
@@ -466,7 +466,7 @@ int Curl_read(struct connectdata *conn, /* connection data */
       nread = sread(sockfd, buf, buffersize);
 
     if(-1 == nread) {
-      int err = Curl_ourerrno();
+      int err = Curl_sockerrno();
 #ifdef WIN32
       if(WSAEWOULDBLOCK == err)
 #else