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/aio.h

@@ -0,0 +1,51 @@
+#ifndef _AIO_H
+#define _AIO_H 1
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/aio.h.html
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#include <fcntl.h>
+#include <time.h>
+#include <signal.h>
+
+#define __need_off_t
+#define __need_pthread_attr_t
+#define __need_size_t
+#define __need_ssize_t
+#include <sys/types.h>
+
+struct aiocb
+{
+	int				aio_fildes;		/* File descriptor. */
+	off_t			aio_offset;		/* File offset. */
+	volatile void*	aio_buf;		/* Location of buffer. */
+	size_t			aio_nbytes;		/* Length of transfer. */
+	int				aio_reqprio;	/* Request priority offset. */
+	struct sigevent	aio_sigevent;	/* Signal number and value. */
+	int				aio_lio_opcode;	/* Operation to be performed. */
+};
+
+#define AIO_ALLDONE			1
+#define AIO_CANCELLED		2
+#define AIO_NOTCANCELLED	3
+#define LIO_NOP				4
+#define LIO_NOWAIT			5
+#define LIO_READ			6
+#define LIO_WAIT			7
+#define LIO_WRITE			8
+
+int		aio_cancel(int fildes, struct aiocb* aiocbp);
+int		aio_error(const struct aiocb* aiocbp);
+int		aio_fsync(int op, struct aiocb* aiocbp);
+int		aio_read(struct aiocb* aiocbp);
+ssize_t	aio_return(struct aiocb* aiocbp);
+int		aio_suspend(const struct aiocb* const list[], int nent, const struct timespec* timeout);
+int		aio_write(struct aiocb* aiocbp);
+int		lio_listio(int mode, struct aiocb* __restrict const list[__restrict], int nent, struct sigevent* __restrict sig);
+
+__END_DECLS
+
+#endif