Please add an option to suppress `LINE` pragma.

This comes from https://github.com/haskell/haddock/issues/1001.

If I understand it correctly, the `LINE` is just for debugging. If Cabal building system could pass an option to c2hs in haddock process to suppress the pragma, the haddock issue should be gone.

Start by tracing where c2hs emits the `LINE` pragma and how command-line options are parsed. Read the linked Haddock issue and inspect the Cabal-to-c2hs invocation context; done means a documented option can suppress the pragma without changing default output.

Written by the indexing model from the issue text.