Continuations and processes

The call/cc implementation has been revamped to make continuations work only within the processes in which they were captured. This is because none of the alternatives to supporting inter-process continuation invocation seemed clean enough or necessary.

What should happen when a process invokes a continuation that was captured by another process? Should it terminate the current process and join with the process to which the continuation belongs? If that's the case, what about the continuations that were captured in the invoking process? Should they be rendered invalid? Would this whole spaghetti be useful or meaningful?

An alternative is to have the continuation invocation finish evaluation in the invoking process and return with a value like nil or T. Doing that, however, means different behaviour when invoking a continuation in the same process it was captured in versus invoking a continuation captured in a different process. In the former case the invocation never completes evaluation whereas in the latter case it does.

Due of all of that, I've disabled invocation of continuations across process boundaries. Any possible use for that can be satisfied by the message passing mechanism (I think), which is simpler and more comprehensible anyway.