Merge pull request #535 from Fanael/master

Make Haskell checkers support literate Haskell.
Update credits and changelog [#535]
Add error filter to increment columns

For use with syntax checkers that emit zero-based columns
Update error filter API docs
Fix pylint error columns
fixup! Add error filter to increment columns
Document base index of error colums in Flycheck
Add test for GHC error to verify GHC error columns
[Fix #536] Merge branch 'clarify-error-columns'

* clarify-error-columns:
  Add test for GHC error to verify GHC error columns
  Document base index of error colums in Flycheck
  fixup! Add error filter to increment columns
  Fix pylint error columns
  Update error filter API docs
  Add error filter to increment columns
Add support for language test selector
Update PHP test case for PHPCS 2
Ignore errors while installing RPM

Don't let sourceforge hiccups break our test suite
Update Texinfo manual

[ci skip]
Fix a typo in CREDITS.rst.