UDP API.

implement sendto()/recvfrom() equivalents.

entirely self-hosted (which avoids problems when building the same
tree on multiple systems - e.g. when you have /home NFS-mounted).

Also saves around 50 bytes in total - not sure why.

allows us to avoid execution loops without having to hack around the
image registration order.

entirely self-hosted (which avoids problems when building the same
tree on multiple systems - e.g. when you have /home NFS-mounted).

Also saves around 50 bytes in total - not sure why.

elsewhere as well.

request(), seek() or deliver_xxx() in order to start the data flow.
Autonomous generators must be genuinely autonomous (having their own
process), or otherwise arrange to be called.  TCP does this by
starting the retry timer immediately.

Add some debugging statements.

request(), seek() or deliver_xxx() in order to start the data flow.
Autonomous generators must be genuinely autonomous (having their own
process), or otherwise arrange to be called.  TCP does this by
starting the retry timer immediately.

Add some debugging statements.

Add reference-counting to processes.

Add timer_running() test.