Cannot compile on mac sierra 10.12.6, -lcrypto failed

[apuex]

libcrypto is deprecated on mac.

[bluca]

Please use https://github.com/zeromq/gsl where maintenance has moved to

@evoskuil it would be probably good to disable creating new issues here

[xtwxy]

@bluca Thank you!

[evoskuil]

@bluca Just saw this :). I don't have the permission :/