Inherit w3m-haddock heading highlight from magit-item-highlight
More thoroughly disable electric-indent

See #377
Revert "More thoroughly disable electric-indent"

This reverts commit 99658ce11e08b8f0825a17247bc84336b6a4cd8c.
Disable indent-tabs-mode in haskell-cabal-mode

"Tabs are not allowed as indentation characters due to a missing
standard interpretation of tab width." - Cabal manual

See #44