Conditionally Packed messages

[ericjbohm]

There are several use cases for messages that can include pointers, if sent within the process boundary they would not require additional allocations or copies. If sent outside, the full copy style message would be created and sent.

Sam notes that message forwarding can create a complication here.

The usage contract would require the user to treat the relevant data being pointed to as read only for the life of the message.