Don't convert Data to [UInt8] when decoding.
Don't convert Data to [UInt8] when decoding.

Calling `[UInt8](data)` results in a copy being made, because it's
treated as a standard collection-to-array initialization. This
introduces a performance penalty, one that can be potentially large (in
both runtime and memory usage) if the data being parsed is large.

tbkka/swift-protobuf,cburrows/swift-protobuf,cburrows/swift-protobuf,cburrows/swift-protobuf,allevato/swift-protobuf,thomasvl/swift-protobuf,tbkka/swift-protobuf,allevato/swift-protobuf,tbkka/swift-protobuf,apple/swift-protobuf,apple/swift-protobuf,allevato/swift-protobuf,cburrows/swift-protobuf,thomasvl/swift-protobuf,allevato/swift-protobuf,allevato/swift-protobuf,thomasvl/swift-protobuf,tbkka/swift-protobuf,thomasvl/swift-protobuf,apple/swift-protobuf,tbkka/swift-protobuf,apple/swift-protobuf,cburrows/swift-protobuf,tbkka/swift-protobuf,cburrows/swift-protobuf,cburrows/swift-protobuf,apple/swift-protobuf,thomasvl/swift-protobuf,tbkka/swift-protobuf,allevato/swift-protobuf,thomasvl/swift-protobuf,thomasvl/swift-protobuf,allevato/swift-protobuf,apple/swift-protobuf,apple/swift-protobuf