ghc-8.0.1: The GHC API

Process Import Decls. See rnImportDecl for a description of what the return types represent. Note: Do the non SOURCE ones first, so that we get a helpful warning for SOURCE ones that are unnecessary
make a GlobalRdrEnv where all the elements point to the same Provenance (useful for "hiding" imports, or imports with no details).
Calculate the ImportAvails induced by an import of a particular interface, but without imp_mods.