Bug 15258: Prevent unused declared variables

Bug 15258: Prevent unused declared variables

Add a perlcritic rule to 00-perlcritic.t to prevent unused declared
variable.

TO TEST:

- Apply the 1st patch (unit test)
- Run the UT:
  prove -v t/00-testcritic.t
- Note that several Perl script fail
- Apply the 2nd patch
- Run the UT, and confirm it passes.

Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
All tests pass successful.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jesse Weaver <jweaver@bywatersolutions.com>