Apply various linter fixes.

Summary: Applied various linter fixes.

Test Plan: Ran `arc unit` to verify things still worked.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9435
Allow `Makefile` files to contain tabs.

Summary: Add an entry to the `.editorconfig` file to allow `Makefile` files to contains tabs over spaces. Without this entry, my editor will automatically convert the tabs to spaces (which `make` does not like).

Test Plan: Opened `./support/xhpast/Makefile` and saved it. Verified that spaces weren't converted to tabs.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9436
Exclude some test data from being linted.

Summary: Currently, `arc lint --apply-patches` will patch some files which contain test data, consequently causing unit tests to file. We should either modify the tests so that they can pass linting and unit tests successfully (if possible), or just exclude them from being linted.

Test Plan: Ran `arc lint --apply-patches` and ensured that these files were not patched.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9437