ghc: 7.8.3

Starts the process of closing [31609](https://github.com/Homebrew/homebrew/issues/31609). The patches previous in :DATA have been merged with this release and consequently are no longer required. There is also currently no dev build available, so that has been scrapped as well.
It is too indented, right? Needs 2 spaces rather than 3? Or does it need removing entirely?