Tweak linting rules.

Summary:
- Removed the default text rule that was applied to all files; it
  produced way too many spurious warnings.  For now, text lint is applied
  to C, Haskell and Shell.  Add more if you care.

- Makefiles and shell scripts had their max line length bumped a healthy
  amount.

A pile of files still fail to lint, so these might even still be too
aggressive.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: none

Reviewers: hvr, austin

Subscribers: simonmar, relrod, ezyang, carter

Differential Revision: https://phabricator.haskell.org/D131