Merge r1893001, r1893002, r1893004 from trunk:

Merge r1893001, r1893002, r1893004 from trunk:

core: Set r->request_time before any logging, mod_unique_id needs it.

* server/protocol.c(read_request_line):
  Move r->request_time initialization before first APLOG_TRACE5,
  ap_log_rerror() may run the generate_log_id hooks and call mod_unique_id
  with no timestamp initialized (zero).

mod_unique_id: Follow up to r1892915: Shorter counter race condition yet.

* modules/metadata/mod_unique_id.c(gen_unique_id):
  Set the counter in network byte order for uuencoding only, allowing for
  simple cur_unique_id.counter++

mod_unique_id: Follow up to r1892915 and r1893002: Atomic counter.

* modules/metadata/mod_unique_id.c(gen_unique_id):
  Use an atomic 32bit counter to close the race condition with threaded MPMs,
  using the lower 16 bits for uuencoding still.

Submitted by: ylavic
Reviewed by: ylavic, rpluem, gbechis

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1893116 13f79535-47bb-0310-9956-ffa450edef68