Revision 1663842

backport.pl: Track a backwards-incompatible Perl language change.

* tools/dist/backport.pl
  (): Explicitly require version v5.10.0.  (Older Perls would not have worked
    anyway since they lack the 'say' feature which this script also requires.)
  (warnings): Disable experimental::smartmatch warnings under Perl v5.20.1
    and earlier.