Allow specifying multiple locations of the same lint error

Summary:
Some errors (duplicate declaration, invalid number of arguments) have more related places.
We need to notify user if he changes any related place.
This could be currently achieved by triggering errors instead of warnings or by including both files in the range (impossible if the locations are in different files) or by issuing multiple errors.
All options are too aggressive.

Test Plan: Issued error on unmodified line with other location on modified line.

Reviewers: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4392
Format whitespace in XHPAST linter

Test Plan: Linted a method named `f_a`.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4405
Add hook after running linters

Summary: This resolves D4380#7 by reverting https://secure.phabricator.com/D4380?vs=9112&id=9123.

Test Plan: Used it in our linters.

Reviewers: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4409
Display other locations of lint errors in console renderer

Test Plan: Created function named `f_a`, manually set other location.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4412
Use assert_instances_of(, 'array')

Summary: To have at least one real callsite.

Test Plan:
  $message = new ArcanistLintMessage();
  $message->setOtherLocations(array());
  $message->setOtherLocations(array(array()));
  $message->setOtherLocations(array(1));

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4419
Merge branch 'master' of http://github.com/facebook/arcanist