Have the configure script look for rlim_t in <sys/resource.h>

That's where POSIX says it should be. Some libcs will include its
definition via <sys/types.h> as well, but musl doesn't.

Signed-off-by: Maarten ter Huurne <maarten@treewalker.org>

--- xinetd-2.3.15.orig/configure	2007-09-20 16:58:27.000000000 +0200
+++ xinetd-2.3.15/configure	2014-09-16 17:20:22.787665449 +0200
@@ -7909,7 +7909,7 @@
 cat confdefs.h >>conftest.$ac_ext
 cat >>conftest.$ac_ext <<_ACEOF
 /* end confdefs.h.  */
-#include <sys/types.h>
+#include <sys/resource.h>
 #if STDC_HEADERS
 #include <stdlib.h>
 #endif
