Security updates for Thursday

Security updates have been issued by Debian (gdal), Fedora (nethack), Mageia (okular, sleuthkit, and webkit2), openSUSE (salt), Oracle (icu, kernel, python-pip, python-virtualenv, and zsh), Red Hat (icu, python-imaging, thunderbird, and zsh), Scientific Linux (icu, python-imaging, and zsh), SUSE (postgresql10), and Ubuntu (apache2).