Move overlay inclusions outside of header protection

Glibc tends to include standard headers with special definitions
that make few declarations or macros visible, this stomps over the
overlay #include_next <> logic.

Based-on-patch-by: Robert Millan <rmh@debian.org>

include/bsd/stdio.h

@@ -24,18 +24,18 @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef LIBBSD_STDIO_H
-#define LIBBSD_STDIO_H
-
-#include <sys/cdefs.h>
-#include <sys/types.h>
-
 #ifdef LIBBSD_OVERLAY
 #include_next <stdio.h>
 #else
 #include <stdio.h>
 #endif
 
+#ifndef LIBBSD_STDIO_H
+#define LIBBSD_STDIO_H
+
+#include <sys/cdefs.h>
+#include <sys/types.h>
+
 __BEGIN_DECLS
 const char *fmtcheck(const char *, const char *);