haddock-2.3.0 literate comments discarded from .lhs input

[Alistair Bayley]

>> i.e. the $httptopdir isn't being expanded, or whatever is meant to happen to it.
>
> Those variables are supposed to be expanded by Cabal, and here on linux i get:
> --read-interface=/usr/local/share/doc/ghc/libraries/base,/usr/local/share/doc/ghc/libraries/base/base.haddock

Really? I searched the cabal source for httptopdir and found nothing,
so I was wondering where it was meant to happen (of course it could be
that my search was incorrectly specified). Do you know which module is
meant to expand this?
Distribution.Simple.InstallDirs.defaultInstallDirs looked a likely
candidate, but no sign of $httptopdir there.

Alistair