Make Send and Receive Methods reentrant safe

[polfeliu]

Right now the send and received methods write to the raw message struct. Those functions are thus not reentrant safe. One way to achieve this would be to define the packing and unpacking union/structures as a type and use them as a local variables of the send and receive methods. This would use stack of the calling thread but would reduce static memory footprint and make them reentrant safe. This may be important for combining different signal send types on the interaction layer.