[AVR] Add release notes for 5.0
[AVR] Add release notes for 5.0


git-svn-id: ee41f7a47e00113e4a3f1d4cbf84f6e482c3caa7@309513 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