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/ndbm.h

@@ -0,0 +1,39 @@
+#ifndef _NDBM_H
+#define _NDBM_H 1
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/ndbm.h.html
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#define DBM_REPLACE 1
+#define DBM_INSERT 0
+
+#define __need_size_t
+#include <stddef.h>
+
+#define __need_mode_t
+#include <sys/types.h>
+
+typedef struct
+{
+	void* dptr;		/* A pointer to the application's data. */
+	size_t dsize;	/* The size of the object pointed to by dptr */
+} datum;
+
+typedef int DBM;
+
+int		dbm_clearerr(DBM* db);
+void	dbm_close(DBM* db);
+int		dbm_delete(DBM* db, datum key);
+int		dbm_error(DBM* db);
+datum	dbm_fetch(DBM* db, datum key);
+datum	dbm_firstkey(DBM* db);
+datum	dbm_nextkey(DBM* db);
+DBM*	dbm_open(const char* file, int open_flags, mode_t file_mode);
+int		dbm_store(DBM* db, datum key, datum content, int store_mode);
+
+__END_DECLS
+
+#endif