fix bus error (misaligned data access) on SPARC in __decodeDouble_Int64
fix bus error (misaligned data access) on SPARC in __decodeDouble_Int64

Reviewers: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D749

(cherry picked from commit 12a03c44c006f142f93980e0dbdfab0f73db042c)

nathyong/microghc-ghc,nathyong/microghc-ghc,nathyong/microghc-ghc,forked-upstream-packages-for-ghcjs/ghc,forked-upstream-packages-for-ghcjs/ghc,nathyong/microghc-ghc,forked-upstream-packages-for-ghcjs/ghc,forked-upstream-packages-for-ghcjs/ghc,nathyong/microghc-ghc,forked-upstream-packages-for-ghcjs/ghc,forked-upstream-packages-for-ghcjs/ghc,nathyong/microghc-ghc,forked-upstream-packages-for-ghcjs/ghc,nathyong/microghc-ghc