Allow stack_ghc linter options to be set

As-current, there appears to be no way to do this according to either ``help ale_haskell``, nor the documentation of ``stack_ghc.vim``. This is a bit odd, because basically all the others allow this (and the ``stack_ghc`` options are very sparse for a linter), and requires some copy-paste redefinitions. Something like ``ale_haskell_stack_ghc_options`` would be great as a settable thing.