* configure.in: Define AP_HAVE_DESIGNATED_INITIALIZER via ap_config.h

so third-party modules don't have to pick up NOTEST_CPPFLAGS to avoid
gcc warnings from http_config.h.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@104642 13f79535-47bb-0310-9956-ffa450edef68