Merge branch 'feat-api-cmds-and-branching'

Implements the programmer-facing API to allow programmatic
specification of a synchronous round. The way in which these put/get
interactions are performed is in an initial shape. Perhaps this will
change in the future.

The second main set of changes is the addion of a 'fork' statement,
which allows explicit forking, and allowing multiple puts/gets over the
same transport link within a single sync round.

Merge branch 'feat-bytecode'

Adds size/alignment/offset computations to the type system and detects
potentially infinite types. If the type is potentially infinite but
contains a union that can break that type loop, then all other variants
of that union are supposed to be allocated on the heap. If the type
is potentially infinite but cannot be broken up, then we throw the
appropriate error.

The size/alignment/offset computations are not yet employed in the
runtime. But prepares Reowolf for a proper bytecode/IR implementation.