[JIRA] (BIT-1506) Bro fails to build on OS X 10.11 (El Capitan) due to OpenSSL header removal

I extended Jon’s fix a bit in topic/vladg/homebrew-openssl. It uses brew --prefix to get Homebrew’s installation prefix, which seems to be the recommended approach.

I also confirmed that Jon’s fix works for me on El Capitan, with Homebrew (works in the sense that I don’t need to pass any command-line arguments to configure).