cooperative threads (uthd)
~~~~~~~~~~~~~~~~~~~~~~~~~~

Non preemptive threads exist for some time.

<ref author of putty, coroutines, knuth>

Making coroutines look like threads is attractive.
Several implementations exist.

<ref two other similar thins>

They miss functions like cancel/join, those functions
are needed by serious programs. (at least, I need them)

So I wrote this set of functions, closely resembling
(protothread implementation from googlecode) but incorporating
more of the POSIX thread interface and having some
standard functions, like asynchronous DNS, socket operatons
(connect, accept, recv, send).