Indexing packages coming with GHC

I was trying to index `bytestring` and found out that it couldn't be done with `haskell-indexer` and also it looks like it breaks package db by unregistering `bytestring` so I needed to run `stack setup --reinstall` to fix the situation. Also it seems to be related to the question from @chrisdone in #79 about `base` but it looks like `base` is not enough and dependencies of GHC which come with it need special treatment. I see in #56 scripts from you @robinp but it looks like it doesn't cover libraries which are in git submodules of GHC repo - why didn't they get indexed? BTW shouldn't those scripts also be included into this repo with some file describing how to index GHC itself (at the moment it's not clear to me where that `/opt/ghc/bin/ghc` come from - probably it's about your custom install of GHC into `/opt/ghc`?)