nl_types.h: explicitly include cdefs.h

This file uses __BEGIN_DECLS/__END_DECLS. When bootstrapping from
Linux/musl, they were missing.

Sponsored by:	https://www.patreon.com/valpackett
Pull Request:	https://github.com/freebsd/freebsd-src/pull/1066

include/nl_types.h

@@ -34,6 +34,7 @@
 #ifndef _NL_TYPES_H_
 #define _NL_TYPES_H_
 
+#include <sys/cdefs.h>
 #include <sys/types.h>
 
 #ifdef _NLS_PRIVATE