Support messages longer than 32 bits

[ericjbohm]

The hard version of this would require supporting longer converse messages without adding overhead to sending (header size) and handling (conditional logic) normal converse messages.

The medium version of this would support a charm build time choice to select larger messages and thereby avoid various overheads at the cost of flexibility.

The "good enough?" version of this would leave message formats themselves out of it and handle this via pipelining techniques to handle fragmentation of a large message into smaller components, then deliver the fully thing at the end.