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/dirent.h

@@ -0,0 +1,45 @@
+#ifndef _DIRENT_H
+#define _DIRENT_H 1
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/dirent.h.html
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#define __need_ino_t
+#include <sys/types.h>
+
+typedef struct __DIR DIR;
+
+#define DT_UNKNOWN	0
+#define DT_REG		1
+#define DT_DIR		2
+#define DT_CHR		3
+#define DT_BLK		4
+#define DT_FIFO		5
+#define DT_SOCK		6
+#define DT_LNK		7
+
+struct dirent
+{
+	ino_t d_ino;			/* File serial number. */
+	unsigned char d_type;	/* File type. One of DT_* definitions. */
+	char d_name[256];		/* Filename string of entry. */
+};
+
+int				alphasort(const struct dirent** d1, const struct dirent** d2);
+int				closedir(DIR* dirp);
+int				dirfd(DIR* dirp);
+DIR*			fdopendir(int fd);
+DIR*			opendir(const char* dirname);
+struct dirent*	readdir(DIR* dirp);
+int				readdir_r(DIR* __restrict dirp, struct dirent* __restrict entry, struct dirent** __restrict result);
+void			rewinddir(DIR* dirp);
+int				scandir(const char* dir, struct dirent*** namelist, int (*sel)(const struct dirent*), int (*compar)(const struct dirent**, const struct dirent**));
+void			seekdir(DIR* dirp, long loc);
+long			telldir(DIR* dirp);
+
+__END_DECLS
+
+#endif