Merge r1821624, r1821625, r1821626, r1821627, r1821629, r1821632, r1821635, r1821639...

Merge r1821624, r1821625, r1821626, r1821627, r1821629, r1821632, r1821635, r1821639, r1821644, r1821647, r1821648, r1821649, r1821650, r1821651, r1821659, r1821660, r1822366, r1822367, r1824381 from trunk:

Shared fdqueue code between MPMs event and worker into mpm_fdqueue.

This first step moves the files server/mpm/event/fdqueue.[ch] to
server/mpm_fdqueue.[ch] (untouched for now, simple svn move).

Will follow up with the necessary changes to mpm_unix.* for common code.

mpm_fdqueue: follow up to r1821624.

And now it's mpm_fdqueue, with minimal #includes.

mpm_fdqueue: follow up to r1821624.

Opacify fdqueue types.

mpm_fdqueue: follow up to r1821624.

Style, no functional change.

mpm_fdqueue: follow up to r1821624.

Rename ap_queue_info_get_idlers() to ap_queue_info_num_idlers().

mpm_fdqueue: follow up to r1821624.

Clear recycled_pools_count in ap_free_idle_pools().

mpm_fdqueue: follow up to r1821624.

Prepare mpm_worker to use common fdqueue.

mpm_worker: follow up to r1821624.

Use common [mpm_]fdqueue.

mpm_fdqueue: follow up to r1821624.

The implemention wants APR_HAS_THREADS too.

mpm_fdqueue: follow up to r1821624.

The code is not part of the API.

mpm_fdqueue: follow up to r1821624.

Fix typo in comment.

mpm_fdqueue: follow up to r1821624.

Cosmetics, 80 cols, no functional change.

mpm_worker: follow up to r1821624.

Free idle pools while stopping.

mpm_fdqueue: follow up to r1821624.

Be explicit in the naming about what's push/pop-ed.

mpm_fdqueue: follow up to r1821624.

Either error matters, simplify code.

mpm_fdqueue: follow up to r1821624.

Make the allocation and zero-ing in ap_queue_init() => ap_queue_create().

mpm_fdqueue: follow up to r1821624.

Export ap_queue_*() fonctions, so that they are accessible from MPMs, but
don't provide "mpm_fdqueue.h" in the API (include/).

mpm_fdqueue: follow up to r1821624.

80 colums.

Follow up to r1821624: CHANGES entry.

Submitted by: ylavic
Reviewed by: ylavic, minfrin, jim

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1824866 13f79535-47bb-0310-9956-ffa450edef68