Fix headers to be inclued alone

See b.android.com/64679 for one of header sys/prctl.h

Change-Id: Ie415ebe2086d2f0190d84fba0c57cc7e1e5822ae

ndk/platforms/android-8/include/fts.h

@@ -35,6 +35,8 @@
 #ifndef	_FTS_H_
 #define	_FTS_H_
 
+#include <sys/types.h>
+
 typedef struct {
 	struct _ftsent *fts_cur;	/* current node */
 	struct _ftsent *fts_child;	/* linked list of children */