Coro-5.0 - coroutine process abstraction

Changes for version 5.0 - 2008-11-20

NEW ARCHITECTURE: use the latest 4.x version if you experience stability issues.
bump API version to 7 - all dependents must be recompiled.
removed timed_* functions - they were not being used anyways and should be replaced by a more generic mechanism - and were annoying to support anyways :)
removed SemaphoreSet's waiter method - use sem method instead.
Coro::Semaphore->adjust didn't correctly wake up enough waiters.
async_pool did free a scalar value twice ("Attempt to unreference...").
fix a longstanding bug where calling terminate on a coro that was waiting for a semaphore that was just becoming available would cause a deadlock (semaphore would get into a state where it was available but waiters were still blocked).
calling throw on a coroutine that is waiting for a semaphore will no longer make it acquire the semaphore (and thus leak a count).
perl's process emulation is now not even theoretically supported anymore.
new functions Coro::rouse_cb and Coro::rouse_wait for easier conversion of callback-style to blocking-style.
new methods $coro->schedule_to and ->cede_to, to specifically schedule or cede to a specific coroutine.
new function Coro::Semaphore::wait.
use named constants in Coro::Channel (Richard Hundt).
directly patch the entersub opcode calling SLF functions (cede, transfer and so on). this does speed up context switching, but more importanly, it frees us from the hardcoded behaviour of entersub, so we might actually be able to return something from those functions and atcually create new ones.
take advantage of __builtin_frame_address on gcc.
expose THX in coroapi (not sure whether this was a wise decision, as "threaded" perls are running at half speed anyways).
implement execute_slf (schedule-like-function) interface that makes it possible to implement schedule-like-functions in XS.
use new SLF interface to massively speed up Coro::EV by roughly a factor of two.
used new SLF interface to massively speed up Coro::Semaphore by a factor of three.
used new SLF interface to speed up Coro::AIO by roughly a factor of four and reduce its memory usage considerably.
implement Coro::SemaphoreSet purely in terms of Coro::Semaphore, for a nice speedup and vastly more correct behaviour. Also implement a new method "sem" to get at the underlying semaphore object.
implement Coro::Channel in terms of Coro::Semaphore, for a moderate (in comparison) 20-40% speedup.
used new SLF interface to reimplement Coro::Signal gaining some unknown (because I was too lazy), but certain, speedup, and also making signals reliable for the first time.
used new SLF interface and other optimisations to speed up async_pool by a factor of two. It also doesn't rely on perl's exception mechanism to exit anymore. The overhead for terminating an async_pool, coro over a normal async is now very small.
sped up coroutine creation/destruction by 40%.
forgot to include Coro/libcoro/README in the dist for all these years.
work around a freebsd pthreads bug (manual testcancel is required as pthread_cond_wait isn't a cancellation point on freebsd).
use new rouse functions to speed up and simplify Coro::BDB.
make "prefer perl native functions" work with threaded perls.
condense Coro::Debug ps output, hint at v and w flags.
(libcoro) lots of minor cleanups and portability improvements.