bug#20960: handling /etc/ssl/certs/ca-bundle.crt by default in emacs

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> Cc: Petr Hracek <phracek@redhat.com>,  20960@debbugs.gnu.org
> Date: Thu, 02 Jul 2015 11:38:25 -0400
> 
> So let's compile a list of the standard places and default to the first
> that exists

Is that really TRT?  I don't use Gnus, but smime.el seems to want a
place to keep certificates of people/organizations from which you get
MIME messages.  How probable it is to find them in the bundles
distributed by the OS?

I thought the user is supposed to collect the certificates for this
purpose, and keep them in this directory.  IOW, these are not
system-wide certificates.

> similar to what gnutls-trustfiles does. (Does these two variables
> duplicate each other?)

gnutls-trustfiles should not be needed, except with old versions of
GnuTLS.  The library now finds and uses the system-provided bundle
automatically (and on Windows the system certificates are not kept in
a disk file).