fix compile breakage with IBM's xlc compiler caused by the

attempt to lose const on progname

strrchr was not the real library function that takes a
const parameter; instead, strrchr was the Apache macro which
makes it clear that const will be lost


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@95900 13f79535-47bb-0310-9956-ffa450edef68

os/unix/unixd.c

@@ -332,7 +332,7 @@ static apr_status_t ap_unix_create_privileged_process(
         return apr_proc_create(newproc, progname, args, env, attr, p);
     }
 
-    argv0 = strrchr(progname, '/');
+    argv0 = ap_strrchr_c(progname, '/');
     /* Allow suexec's "/" check to succeed */
     if (argv0 != NULL) {
         argv0++;