[boost] coroutine library?

Has anyone considered developing/submitting a coroutine library for boost? I've been developing C/C++ for years, and only just discovered how incredibly useful userspace single-threaded multitasking is, if you want to avoid the huge overhead of POSIX threads, and don't mind having to explicitly yield to other threads in your code (indeed, this makes the issues of concurrency and synchronization between threads just much simpler). I've written a wrapper around PCL (http://www.xmailserver.org/libpcl.html) and have since found it to be at least as useful as many of the other boost libraries in my last few projects, in particular in a select-driven single-thread socket server which i am working on now.