Avoids errors like the following:
In file included from ./include/openvswitch/types.h:21,
from ./lib/vconn.h:21,
from tests/test-vconn.c:18:
/usr/include/sys/types.h:52: error: conflicting types for 'ino_t'
/usr/include/linux/types.h:14: error: previous declaration of 'ino_t' was here
/usr/include/sys/types.h:62: error: conflicting types for 'dev_t'
/usr/include/linux/types.h:13: error: previous declaration of 'dev_t' was here
/usr/include/sys/types.h:67: error: conflicting types for 'gid_t'
/usr/include/linux/types.h:27: error: previous declaration of 'gid_t' was here
/usr/include/sys/types.h:72: error: conflicting types for 'mode_t'
/usr/include/linux/types.h:15: error: previous declaration of 'mode_t' was here
/usr/include/sys/types.h:77: error: conflicting types for 'nlink_t'
/usr/include/linux/types.h:16: error: previous declaration of 'nlink_t' was here
/usr/include/sys/types.h:82: error: conflicting types for 'uid_t'
/usr/include/linux/types.h:26: error: previous declaration of 'uid_t' was here
/usr/include/sys/types.h:90: error: conflicting types for 'off_t'
/usr/include/linux/types.h:17: error: previous declaration of 'off_t' was here
* <linux/types.h> to allow <linux/openvswitch.h> to work, that is, it defines
* the __u<N> and __be<N> types. */
-#if __KERNEL__ || HAVE_LINUX_TYPES_H
+#ifdef __KERNEL__
+#include_next <linux/types.h>
+#elif defined(HAVE_LINUX_TYPES_H)
+/* With some combinations of kernel and userspace headers, including both
+ * <sys/types.h> and <linux/types.h> only works if you do so in that order, so
+ * force it. */
+#include <sys/types.h>
#include_next <linux/types.h>
#else /* no <linux/types.h> */
#include <stdint.h>