BuildSystem: Move all userpace libraries under the userspace directory

As the number of libraries is increasing, root directory starts to
expand. This adds better organization for libraries

userspace/libraries/LibC/include/sched.h

@@ -0,0 +1,40 @@
+#ifndef _SCHED_H
+#define _SCHED_H 1
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sched.h.html
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#include <time.h>
+
+#define __need_pid_t
+#include <sys/types.h>
+
+struct sched_param
+{
+	int				sched_priority;			/* Process or thread execution scheduling priority. */
+	int				sched_ss_low_priority;  /* Low scheduling priority for sporadic server. */
+	struct timespec	sched_ss_repl_period;	/* Replenishment period for sporadic server. */
+	struct timespec	sched_ss_init_budget;	/* Initial budget for sporadic server. */
+	int				sched_ss_max_repl;		/* Maximum pending replenishments for sporadic server. */
+};
+
+#define SCHED_FIFO		1
+#define SCHED_RR		2
+#define SCHED_SPORADIC	3
+#define SCHED_OTHER		4
+
+int sched_get_priority_max(int policy);
+int sched_get_priority_min(int policy);
+int sched_getparam(pid_t pid, struct sched_param* param);
+int sched_getscheduler(pid_t pid);
+int sched_rr_get_interval(pid_t pid, struct timespec* interval);
+int sched_setparam(pid_t pid, const struct sched_param* param);
+int sched_setscheduler(pid_t pid, int, const struct sched_param* param);
+int sched_yield(void);
+
+__END_DECLS
+
+#endif