GnuTLS integration manual patch needs review

[Ted Zlatanov]

The patch here suggests some testing methods to ensure (with the current
Emacs) that the GnuTLS integration works, and to secure things if the
integration is not available. I'd like some review, please, before I
push it into master.

Thanks
Ted

diff --git a/doc/misc/emacs-gnutls.texi b/doc/misc/emacs-gnutls.texi
index 4f6ef01..a40aa67 100644
--- a/doc/misc/emacs-gnutls.texi
+++ b/doc/misc/emacs-gnutls.texi
@@ -97,6 +97,27 @@
 This function returns @code{t} if GnuTLS is available in this instance of 
Emacs.
 @end defun
 
+If you're on a platform without the GnuTLS integration support, you
+can try using the following settings, but they are strongly
+discouraged and will have no effect in a future Emacs release (the
+exact release where that will happen is as of yet unknown).  Again,
+these settings are discouraged!
+
+(You may want to replace the @code{python -m certifi} there with a
+static path to your CA trust bundle, for example,
address@hidden/etc/ssl/certs/ca-certificates.crt}.
address@hidden://pypi.python.org/pypi/certifi} is a Python package that
+distributes a root CA trust bundle for other programs to use.  If you
+don't know what any of this means, you should absolutely not be using
+these settings.  Did we mention they are discouraged?)
+
address@hidden
+ '(tls-checktrust t)
+ '(tls-program
+   (quote
+    ("gnutls-cli --x509cafile \"$(python -m certifi)\" -p %p %h")))
address@hidden lisp
+
 Oh, but sometimes things go wrong.  Budgets aren't balanced,
 television ads lie, and even TLS and SSL connections can fail to work
 properly.  Well, there's something to be done in the last case.
@@ -108,6 +129,17 @@
 information.
 @end defvar
 
+You can check your SSL/TLS connectivity with the built-in Emacs URL
+package.  Switch to the @code{*scratch*} buffer and run:
+
address@hidden
+(require 'url)
+;; valid certificate, you should check out Let's Encrypt!
+(url-insert-file-contents "https://letsencrypt.org/";)
+;; invalid certificate authority, abort
+(url-insert-file-contents "https://www.financialcryptography.com/";)
address@hidden lisp
+
 @defvar gnutls-algorithm-priority
 The @code{gnutls-algorithm-priority} variable sets the GnuTLS priority
 string.  This is global, not per host name (although