Include AC_INCLUDES_DEFAULT (which includes <sys/types.h>), in addition

to <socket.h>, when doing the test for socklen_t. Apparently OpenBSD has
it in <sys/types.h> and it causes a build failure later if we detect
that the type is not present.

libdnet-stripped/configure

@@ -14033,6 +14033,7 @@ _ACEOF
 cat confdefs.h >>conftest.$ac_ext
 cat >>conftest.$ac_ext <<_ACEOF
 /* end confdefs.h.  */
+$ac_includes_default
 #include <sys/socket.h>
 
 int
@@ -14068,6 +14069,7 @@ _ACEOF
 cat confdefs.h >>conftest.$ac_ext
 cat >>conftest.$ac_ext <<_ACEOF
 /* end confdefs.h.  */
+$ac_includes_default
 #include <sys/socket.h>
 
 int

libdnet-stripped/configure.in

@@ -194,7 +194,8 @@ AC_PROG_GCC_TRADITIONAL
 if test "$GCC" = yes ; then
    	CFLAGS="$CFLAGS -Wall"
 fi
-AC_CHECK_TYPES([socklen_t], [], [], [#include <sys/socket.h>])
+AC_CHECK_TYPES([socklen_t], [], [], [AC_INCLUDES_DEFAULT
+#include <sys/socket.h>])
 
 dnl Checks for library functions.
 AC_FUNC_MEMCMP