Adds back zeromq v3.x. The API in 4.x is not backward-compatible.

Copied from Homebrew/homebrew@c356bf77400b0d1ca83431330bf0750741fc24b1 in the main repo.

https://github.com/Homebrew/homebrew/commit/c356bf77400b0d1ca83431330bf0750741fc24b1