GHC 9 compatibility fixes

[utdemir]

This patch contains some minor changes to get syb compile with the current GHC HEAD (soon to be GHC 9).

• It imports 'unsafeCoerce#' from 'GHC.Exts': https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.0#base-415
• Eta-expand some fields: https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.0#base-415
• Remove whitespace after a bang pattern: https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.0#whitespace-sensitive-and-

I tried to choose the backwards compatible options, but I haven't tried this with older compiler versions.

[ethercrow]

@dreixel please have a look.

[dreixel]

I don't really maintain this anymore, but I believe @sergv has taken over.