Make <sys/timeb.h> work without including <sys/types.h>.

According to the last POSIX specification that contained <sys/timeb.h>,
this header should also typedef time_t properly. Also add a proper
comment to the final #endif.

sys/sys/timeb.h

@@ -38,6 +38,13 @@
 #ifndef _SYS_TIMEB_H_
 #define _SYS_TIMEB_H_
 
+#include <sys/_types.h>
+
+#ifndef _TIME_T_DECLARED
+typedef	__time_t	time_t;
+#define	_TIME_T_DECLARED
+#endif
+
 /* The ftime(2) system call structure -- deprecated. */
 struct timeb {
 	time_t	time;			/* seconds since the Epoch */
@@ -54,4 +61,4 @@ int ftime(struct timeb *);
 __END_DECLS
 #endif /* _KERNEL */
 
-#endif
+#endif /* !_SYS_TIMEB_H_ */