todo after releases

Things to do after releases are made

Update default GHC version for new Trac tickets.
Update Commentary/Libraries/VersionHistory.
Delete __GLASGOW_HASKELL__ ifdefs for versions of ghc older than the previous 2 major releases. Something like (add versions which you want to keep the ifdefs for, remove versions you want to delete them for):
```
git grep -l GLASGOW_ | grep -v 'users_guide' | xargs grep GLASGOW_ | grep -v '712\|711\|710\|709\|708'
```