[commit: ghc] wip/no-exnstr's head updated: Merge branch 'master' into wip/no-exnstr (a1cc538)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

Branch 'wip/no-exnstr' now includes:

     09128f3 users guide: Note improved constant folding in 8.6 release notes
     0e37361 Revert "Enhanced constant folding"
     90283b5 rts: Comment wibbles
     4d30bc8 Remove markSignalHandlers
     a1cc538 Merge branch 'master' into wip/no-exnstr