clamav: Update to 0.99.3

clamav: Update to 0.99.3

Excerpt from 'README':

"ClamAV 0.99.3 is a hotfix release to patch a set of vulnerabilities.

- fixes for the following CVE's: CVE-2017-6418, CVE-2017-6420,
  CVE-2017-12374, CVE-2017-12375, CVE-2017-12376, CVE-2017-12377,
  CVE-2017-12378, CVE-2017-12379, CVE-2017-12380.
- also included are 2 minor fixes to properly detect openssl install
  locations on FreeBSD 11, and prevent false warnings about zlib 1.2.1#
  version numbers."

For details see:
http://blog.clamav.net/2018/01/clamav-0993-has-been-released.html

Best,
Matthias

Signed-off-by: Matthias Fischer <matthias.fischer@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>