[RelNotes,AArch64] Mention improved instruction fusion and fun alignment.
[RelNotes,AArch64] Mention improved instruction fusion and fun alignment.

Reviewers: t.p.northover, hans, kristof.beyls

Reviewed By: hans

Subscribers: aemerson, rengolin, llvm-commits

Differential Revision: https://reviews.llvm.org/D36965

git-svn-id: ee41f7a47e00113e4a3f1d4cbf84f6e482c3caa7@311539 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm