!6238: Doc: warnings: add `:since:` fields for warnings of GHC 6/7/8 · Merge requests · Glasgow Haskell Compiler / GHC

Andreas Abel requested to merge abel/ghc:issue18087 into master Jul 25, 2021

Addressing #18087, adding since fields for many warnings introduced in GHC since 6.0.

This PR needs backporting to:

Edited Jul 26, 2021 by Andreas Abel

Doc: warnings: add `:since:` fields for warnings of GHC 6/7/8