Implement a Perl Critic test script

[adamk]

Implement a Perl::Critic test script to be run under RELEASE_TESTING only. Do not add dependencies to the project for this.

The test script should run against the perlcritic.ini file already written into the t directory, and should run with the -only option, so that NO critic policies are enforced initially.

We will add policies one at a time to the config file once the test script is in place.

[rhebus]

this is satisfied by xt/critic-{core,util}.t isn't it? The only thing missing is the '-only' option.