* Make EXAMPLE_LOG_EACH compiler directive settable on command line

* Make EXAMPLE_LOG_EACH compiler directive settable on command line
* Clean up introductory comments for hook handler declarations, explain about
  RUN_ALL, RUN_FIRST in one single place, remove leftover comments from 1.3
* Place trace entry for quick_handler in request context
* Found every hook declaration in the source by running

  find . -name \*.[ch] | xargs grep -E -A 3  \
    "AP_IMPLEMENT_(OPTIONAL_|)HOOK_(VOID|RUN_ALL|RUN_FIRST)"

  from top of source tree; implemented handler for everything that turned
  up.

Next up: bring comments in line with introduction, clean up existing comments;
re-design trace mechanism to stop messing with globals after server may
start threads.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@479099 13f79535-47bb-0310-9956-ffa450edef68