s/curret/current/

* use SSL/TLS where available
* follow permanent redirects

use \fI-style instead of .BR for references

and a conversion to markdown. Removed the lib/README.* files. The idea
being to move toward having INTERNALS as the one and only "book" of
internals documentation.

Added a TOC to top of the document.

Stop linking to the curl.haxx.se anchor pages, they are usually only
themselves pointers to the real page so better point there directly
instead.

The protocol is named "HTTP/2" after all. It is an alias for the
existing CURL_HTTP_VERSION_2_0 enum.

Prior to this change any-domain cookies (cookies without a domain that
are sent to any domain) were exported with domain name "unknown".

Bug: https://github.com/bagder/curl/issues/292

Bug: http://curl.haxx.se/mail/lib-2015-06/0001.html
Reported-by: Rafayel Mkrtchyan