Fri Nov 27 11:23:31 CET 2009

Coroutine interface C <-> VM

Requires: "yield" signal that preserves current continuation.  This is
already +- implememented with the MT continuation.

Currently I don't see how to do this.  Something isn't right.

Yield should behave as a primitive: the re-entry from scheme behaves
as the return value of the sc_yield() primitive.