Add <IfDirective> and <IfSection>:

* server/core.c
  (test_ifdirective_section, test_ifsection_section): New callbacks.
  (core_cmds): Define new directives.

* include/http_config.h, server/config.c (ap_exists_directive):
  New function.

* include/ap_mmn.h: Bump MMN minor for above.

* docs/manual/mod/core.xml: Add docs.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1786110 13f79535-47bb-0310-9956-ffa450edef68