refresh CA certificates

In order to resolve the TURKTRUST compromise, and to catch any other
issues that may have fallen through the cracks, I'm changing
the certificate bundle to match the /etc/pki/tls/certs/ca-bundle.crt
on my system, from Fedora 18's package ca-certificates-2012.87-1.fc18.noarch.

See #1102 for some discussion.

As per `yum info`, the certificate file is public-domain:

$ sudo yum info ca-certificates
Loaded plugins: changelog, langpacks, presto, refresh-packagekit
Installed Packages
Name        : ca-certificates
Arch        : noarch
Version     : 2012.87
Release     : 1.fc18
Size        : 1.6 M
Repo        : installed
From repo   : updates
Summary     : The Mozilla CA root certificate bundle
URL         : http://www.mozilla.org/
License     : Public Domain
Description : This package contains the set of CA certificates chosen by the
            : Mozilla Foundation for use with the Internet PKI.