williammuji

Fix multiple simultaneous requests to same URL cause coredump

1

**1. BUILD_TYPE=debug** examples/curl/mcurl.cc: ``` curl::RequestPtr req = curl.getUrl("https://chenshuo.com"); req->setDataCallback(onData); req->setDoneCallback(done); curl::RequestPtr req2 = curl.getUrl("https://chenshuo.com"); // req2->allowRedirect(5); req2->setDataCallback(onData); req2->setDoneCallback(done); curl::RequestPtr req3 = curl.getUrl("https://chenshuo.com"); // req3->allowRedirect(5); req3->setDataCallback(onData); req3->setDoneCallback(done); ``` Error output: >...