Autogenerated imports create a lot of unused import warnings

[jgrosso]

The user shouldn't be bothered by the warnings of the form:

<file path>: warning: [-Wunused-imports]
    The qualified import of ‘Prelude’ is redundant
      except perhaps to import instances from ‘Prelude’
    To import instances alone, use: import Prelude()
  |
2 | import qualified Prelude as GHCPrelude
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

<file path>:3:1: warning: [-Wunused-imports]
    The qualified import of ‘Axel.Parse.AST’ is redundant
      except perhaps to import instances from ‘Axel.Parse.AST’
    To import instances alone, use: import Axel.Parse.AST()
  |
3 | import qualified Axel.Parse.AST as AST
  | ^^

These modules are auto-imported by Axel, and thus the user has no way to fix the warnings anyway.

Two potential solutions are:

1. Filter such warnings out of GHC-generated output. Easier(?), but hackier.
2. Avoid auto-importing these modules if they're not actually used in the files in question (e.g. there are no quotations in the file).