Log Message:
Update audit-packages to 1.25.

+ get rid of unnecessary awk invocation in audit-packages, use shell
  construction instead, pointed out by enami tsugutomo. Cuts system and
  user execution times for audit-packages in half.
+ add (4-clause) licences to audit-packages and download-vulnerability-list
+ check integrity of pkg-vulnerabilities file in audit-packages by using
  the same construct as in download-vulnerability-list
+ CSE in error checking in audit-packages
+ properly terminate a case expression in download-vulnerability-list