Release 2.9.3

[andreasabel]

Release candidate:

• finish testing
• write release notes
• upload to hackage: see https://hackage.haskell.org/package/BNFC-2.9.3/candidate
• v2.9.3-rc release tag
• github release
• linux binary
• win binary
• mac package
• announce on mailing list

Release BNFC-2.9.3:

• finish testing
• write release notes
• upload to hackage
• v2.9.3 release tag
• github release
• linux binaries
• win binary
• mac package
• readthedocs
• update bnfc webpages https://github.com/BNFC/bnfc.github.com
• announce on mailing list
• bump master to 2.9.4
  • source/changelog
  • source/BNFC.spec
  • source/BNFC.cabal
  • testing/bnfc-system-tests.cabal
  • docs/conf.py