prepare struct sched_param for change in time_t definition

the time_t members in struct sched_param are just reserved space to
preserve size and alignment. when time_t changes to 64-bit on 32-bit
archs, this structure should not change.

make definition conditional on _REDIR_TIME64 to match the size of the
old time_t, which can be assumed to be long if _REDIR_TIME64 is
defined.

Author: richfelker

include/sched.h

@@ -19,10 +19,14 @@ extern "C" {
 struct sched_param {
 	int sched_priority;
 	int __reserved1;
+#if _REDIR_TIME64
+	long __reserved2[4];
+#else
 	struct {
 		time_t __reserved1;
 		long __reserved2;
 	} __reserved2[2];
+#endif
 	int __reserved3;
 };