If the Script-and-Regex linter captures no "line" text, treat the message as affecting the entire file
If the Script-and-Regex linter captures no "line" text, treat the message as affecting the entire file

Summary: Fixes T10124.

Test Plan:
Added this "linter" to `.arclint`:

```
    "thing": {
      "type": "script-and-regex",
      "script-and-regex.script": "echo every file is very bad #",
      "script-and-regex.regex": "/^(?P<message>.*)/"
    }
```

...to produce this diff. Also made a variant of it which matches lines to make sure that still works.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10124

Differential Revision: https://secure.phabricator.com/D15000

folsom-labs/arcanist,chundongwang/arcanist,coursera/arcanist,r4nt/arcanist,wikimedia/phabricator-arcanist,folsom-labs/arcanist,phacility/arcanist,calblueprint/arcanist,aik099/arcanist,Khan/arcanist,coursera/arcanist,r4nt/arcanist,folsom-labs/arcanist,fivestars/arcanist,zhihu/arcanist,phacility/arcanist,aik099/arcanist,fivestars/arcanist,codelabs-ch/arcanist,coursera/arcanist,haskell-infra/arcanist,uber/arcanist,zhihu/arcanist,codelabs-ch/arcanist,calblueprint/arcanist,aik099/arcanist,folsom-labs/arcanist,wikimedia/phabricator-arcanist,Khan/arcanist,r4nt/arcanist,chundongwang/arcanist,r4nt/arcanist,fivestars/arcanist,uber/arcanist,coursera/arcanist,calblueprint/arcanist,codelabs-ch/arcanist,wikimedia/phabricator-arcanist,fivestars/arcanist,Khan/arcanist,phacility/arcanist,calblueprint/arcanist,haskell-infra/arcanist,uber/arcanist,wikimedia/phabricator-arcanist,codelabs-ch/arcanist,codelabs-ch/arcanist,Khan/arcanist,haskell-infra/arcanist,zhihu/arcanist,aik099/arcanist,phacility/arcanist,phacility/arcanist,chundongwang/arcanist,uber/arcanist,haskell-infra/arcanist,zhihu/arcanist,chundongwang/arcanist