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.
There doesn't actually seem to be a new testsuite release to match the new ghc release. Should I leave it in or just axe the whole thing?