mod_systemd: Axe APR_OPTIONAL_FN redeclarations to avoid compiler warning.

ap_find_systemd_socket() and ap_systemd_listen_fds() are already declared in
"ap_listen.h", so just include them.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1916312 13f79535-47bb-0310-9956-ffa450edef68
(cherry picked from commit e343347)

Author: ylavic

modules/arch/unix/mod_systemd.c

@@ -18,6 +18,7 @@
 #include <stdint.h>
 #include <ap_config.h>
 #include "ap_mpm.h"
+#include "ap_listen.h"
 #include <http_core.h>
 #include <httpd.h>
 #include <http_log.h>
@@ -34,12 +35,6 @@
 #include <unistd.h>
 #endif
 
-APR_DECLARE_OPTIONAL_FN(int,
-                        ap_find_systemd_socket, (process_rec *, apr_port_t));
-
-APR_DECLARE_OPTIONAL_FN(int,
-                        ap_systemd_listen_fds, (int));
-
 static int systemd_pre_config(apr_pool_t *pconf, apr_pool_t *plog,
                               apr_pool_t *ptemp)
 {