check PKGBASEDIR, ghc bootstrapping, ghc_reindex_haddock nop, drop ghc-*-doc provides
    
    - ghc-deps.sh: check PKGBASEDIR exists to avoid warning for bin package
    - abort cabal_configure if ghc is not self-bootstrapped
    - make ghc_reindex_haddock a safe no-op
    - no longer provide ghc-*-doc
    - no longer run ghc_reindex_haddock in ghc-*-devel scripts