Curl_proxyCONNECT: clear 'rewindaftersend' on success

After having done a POST over a CONNECT request, the 'rewindaftersend'
boolean could be holding the previous value which could lead to badness.

This should be tested for in a new test case!

Bug: https://groups.google.com/d/msg/msysgit/B31LNftR4BI/KhRTz0iuGmUJ

lib/http_proxy.c

@@ -560,6 +560,8 @@ CURLcode Curl_proxyCONNECT(struct connectdata *conn,
 
   infof (data, "Proxy replied OK to CONNECT request\n");
   data->req.ignorebody = FALSE; /* put it (back) to non-ignore state */
+  conn->bits.rewindaftersend = FALSE; /* make sure this isn't set for the
+                                         document request  */
   return CURLE_OK;
 }
 #endif /* CURL_DISABLE_PROXY */