Add optional openssl support

The PR includes a commented out option in "build-all.sh" for including OpenSSL binaries.

It clones this repo and builds it: https://github.com/Zen-CODE/ios-openssl

One thing that I am not sure about is which architectures we need to build for? See lines 85 to 89 of: https://github.com/Zen-CODE/ios-openssl/blob/master/build.sh. Please advise.