Text

Add `Data.Text` benchmark. More interestingly, this branch changes two things in liquidhaskell:

1. we now query GHC for the path to an imported Hs/Lhs file, and use the `-i` flag as a backup.
2. all calls to `dropModuleNames` have been removed because they make cross-module verification much more difficult.

There are still things that could be done in Text, but ByteString needs the cross-module stuff for ByteString.Lazy.

Note: this branch depends on https://github.com/ucsd-progsys/liquid-fixpoint/pull/14