Ensure header files using __BEGIN_DECLS include sys/cdefs.h.

We keep fixing these one-by-one; let's fix them all at once.

Found thus:

  find . -name *.h | xargs grep -L sys/cdefs.h | xargs grep -l BEGIN_DECL | xargs grep -L sys/types

Change-Id: I188842aa2484dc6176e96556d57c38a0f785b59b

libc/include/sys/timeb.h

@@ -28,6 +28,7 @@
 #ifndef _SYS_TIMEB_H
 #define _SYS_TIMEB_H
 
+#include <sys/cdefs.h>
 #include <sys/time.h>
 
 __BEGIN_DECLS