This is what it's meant all along, but now we actually have multiple
implementations, it's clearer to use the name of the library.

As an alternative to OpenSSL when we're on OS X. This one can actually
take advantage of stacking the streams.

This allows users to specify self-signed certificates, or to provide their
own certificate stores on limited platforms such as mobile phones.

This survived the last round of culling, as the signature is only in the
comments.

Move system directory cache out of utils