You used to only be able to enable Opt_WarnDodgyImports with -W or -Wall.
This patch adds the flag to en/disable it by name.
(DodgyImports == importing T(..) when only T is exported).
-- these -f<blah> flags can all be reversed with -fno-<blah>
fFlags = [
+ ( "warn-dodgy-imports", Opt_WarnDodgyImports ),
( "warn-duplicate-exports", Opt_WarnDuplicateExports ),
( "warn-hi-shadowing", Opt_WarnHiShadows ),
( "warn-implicit-prelude", Opt_WarnImplicitPrelude ),