Also document their specific formats. Closes #502
These constants have the same values, but X509_FILETYPE_DEFAULT doesn't work in the Ssl methods and using the SSL_* names is a bit less confusing.
There was previously a lot of behind the scenes magic. We now bind much more directly to the relevant functions. Also remove APN support. That protocol is supersceded by ALPN - let's see if anyone actually needs to use it.
Steven Fackler