Merge r1842010, r1841225, r1862039, r1862040, r1862042 from trunk:

Merge r1842010, r1841225, r1862039, r1862040, r1862042 from trunk:

* dav_stream_response processes data that has been allocated from the propdb
  pool. Hence close the propdb *after* dav_stream_response which clears thei
  probdb pool.

* Doing a PROPFIND on a large collection e.g. 50.000 elements can easily
  consume 1 GB of memory as the subrequests and propdb pools are not
  destroyed and cleared after each element was handled.
  Do this now. There is one case in dav_get_props where elem->priv
  lives longer then the propdb pool. In this case allocate from r->pool.
  Furthermore also recycle propdb's which allows to clear the propdb's
  pools instead of destroying them and creating them again.

Simplify handling of short-lived pool for dav_propdb in mod_dav.  No
functional change.

* modules/dav/main/props.c (dav_popen_propdb): Rename from
  dav_open_propdb, take a pool argument.
  (dav_open_propdb): Reimplement in terms of above, using
  r->pool.
  (dav_propfind_walker): Switch to using dav_open_propdb
  with scratchpool.

* modules/dav/main/props.c (dav_do_prop_subreq): Allocate escaped URI
  out of propdb pool, fixing small per-resource leak during a PROPFIND
  walk.

Submitted by: jorton, rpluem

* modules/dav/main/mod_dav.c (dav_send_multistatus): Tag the pool.

Reviewed by: rpluem, jorton, jim

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1862410 13f79535-47bb-0310-9956-ffa450edef68