CmmLayoutStack: Add unwind information on stack fixups
CmmLayoutStack: Add unwind information on stack fixups

Currently stack fixup blocks don't include unwinding information,
leaving a small window where our unwinding information is incorrect. Fix
this by adding unwinding information to emitted fixup blocks.

Reviewers: scpmw, simonmar, austin

Reviewed By: simonmar

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2742

ezyang/ghc,shlevy/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,sdiehl/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,ezyang/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,shlevy/ghc