- Bug report #2416182 titled "crash in ConnectionExists when using

  duphandle+curl_mutli" (http://curl.haxx.se/bug/view.cgi?id=2416182) showed
  that curl_easy_duphandle() wrongly also copied the pointer to the connection
  cache, which was plain wrong and caused a segfault if the handle would be
  used in a different multi handle than the handle it was duplicated from.