#3520 - fixing putLongParts in ByteStringBuilder and adding tests
Fixing dead code in MessageContainerSerializer.scala
Merge pull request #1621 from akka/wip-3520-fix-putLongParts-in-ByteStringBuilder-√

 #3520 - fixing putLongParts in ByteStringBuilder and adding tests
Merge remote-tracking branch upstream/$:{upbranch}