Packaudit: switch to Subversion
- use links to Subversion tree, HTTPS-flavored ones;
- extract revision using Subversion format of $FreeBSD$;
- refuse to work with vuln.xml that comes from CVS:
automated exporter is switched off, so this source of
vulnerabilities is stale.
Reviewed by: simon, bz (partly), gavin
Approved by: portmgr (tabthorpe), so (des), secteam (simon)