Revert Paul's lock free circular queue changes done on MPM-event.

Revert Paul's lock free circular queue changes done on MPM-event.
The changes have been moved to branches/mpm-event-optimization.

This puts trunk's MPM-event back to the state of 2.4.x, except for serf
support.

The following commits are reverted:
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r1203404 | trawick | 2011-11-17 23:48:35 +0100

event no longer requires APR_POLLSET_THREADSAFE, or any
other non-standard feature (all but OS/2 have APR_POLLSET_WAKEABLE)

config-foo: don't require thread-safe pollset in order to
            build event

event.c: don't stress APR_ENOTIMPL in apr_pollset_create errors;
         just give the standard "check system or user limits"
         message

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r1203858 | trawick | 2011-11-18 22:39:33 +0100

follow up to r1202257 -- perform normal wakeup processing when
APR_EINTR is seen from apr_pollset_poll(), with expectation that
it was triggered by apr_pollset_wakeup()

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r1202395 | trawick | 2011-11-15 20:38:31 +0100

spellcheck r1202258

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r1202329 | pquerna | 2011-11-15 18:47:33 +0100

Calculate the power of two size of the buffer before allocating it.

Spotted by: Rüdiger Plüm

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r1202259 | pquerna | 2011-11-15 16:52:59 +0100

Use apr_pollset_wakeup to ensure that the listener thread will process most enqueue'd events quickly

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r1202258 | pquerna | 2011-11-15 16:52:00 +0100

Because the pollset is now only mutated from the event thread, we no longer need the APR_POLLSET_THREADSAFE flag for the event_pollset

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r1202257 | pquerna | 2011-11-15 16:51:03 +0100

Create a new lock free circular queue, and use it in the EventMPM to remove the timeout mutex that was wrapping both timeout queue operations and pollset operations.

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r1202256 | pquerna | 2011-11-15 16:50:09 +0100

Instead of disabling the listening sockets from the pollset when under load, just stop calling the accept call, but leave the sockets in the pollset.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1293426 13f79535-47bb-0310-9956-ffa450edef68