appveyor: image already had openssl installed Fixes messages like "Version mismatch for openssl: compiled with 1000201f but running with 1000208f" [1]. According to next link: http://help.appveyor.com/discussions/questions/1132-openssl-installation-issues Refs: appveyor/ci#576 [1]: https://ci.appveyor.com/project/azat/libevent/build/2.1.5.95/job/dcy9cfoj3rfo4gdh