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/sys/sem.h

@@ -0,0 +1,54 @@
+#ifndef _SYS_SEM_H
+#define _SYS_SEM_H 1
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_sem.h.html
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#define __need_pid_t
+#define __need_size_t
+#define __need_time_t
+#include <sys/types.h>
+
+#include <sys/ipc.h>
+
+#define SEM_UNDO 1
+
+#define GETNCNT	0
+#define GETPID	1
+#define GETVAL	2
+#define GETALL	3
+#define GETZCNT	4
+#define SETVAL	5
+#define SETALL	6
+
+struct semid_ds
+{
+	struct ipc_perm	sem_perm;	/* Operation permission structure. */
+	unsigned short	sem_nsems;	/* Number of semaphores in set. */
+	time_t			sem_otime;	/* Last semop() time. */
+	time_t			sem_ctime;	/* Last time changed by semctl(). */
+};
+
+// FIXME: A semaphore shall be represented by an anonymous structure, which shall include the following members:
+// unsigned short	semval;		/* Semaphore value. */
+// pid_t			sempid;		/* Process ID of last operation. */
+// unsigned short	semncnt;	/* Number of processes waiting for semval to become greater than current value. */
+// unsigned short	semzcnt;	/* Number of processes waiting for semval to become 0. */
+
+struct sembuf
+{
+	unsigned short	sem_num;	/* Semaphore number. */
+	short			sem_op;		/* Semaphore operation. */
+	short			sem_flg;	/* Operation flags. */
+};
+
+int   semctl(int, int, int, ...);
+int   semget(key_t, int, int);
+int   semop(int, struct sembuf *, size_t);
+
+__END_DECLS
+
+#endif