Remove duplicate implementations of conditional section function. No

Remove duplicate implementations of conditional section function.  No
functional change.

* server/core.c (start_cond_section): Factor out from start_if*.
  Adjust to use apr_strmemdup.
  (test_ifmod_section, test_iffile_section, test_ifdefine_section):
  Move container-specific tests into callbacks from start_if*.
  (core_cmds): Adjust <IfFile, <IfDefine, <IfModule to use
  start_cond_section with callbacks.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1785943 13f79535-47bb-0310-9956-ffa450edef68