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/pwd.h

@@ -0,0 +1,34 @@
+#ifndef _PWD_H
+#define _PWD_H 1
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/pwd.h.html
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#define __need_gid_t
+#define __need_uid_t
+#define __need_size_t
+#include <sys/types.h>
+
+struct passwd
+{
+	char*	pw_name;	/* User's login name. */
+	uid_t	pw_uid;		/* Numerical user ID. */
+	gid_t	pw_gid;		/* Numerical group ID. */
+	char*	pw_dir;		/* Initial working directory. */
+	char*	pw_shell;	/* Program to use as shell. */
+};
+
+void			endpwent(void);
+struct passwd*	getpwent(void);
+struct passwd*	getpwnam(const char* name);
+int				getpwnam_r(const char* name, struct passwd* pwd, char* buffer, size_t bufsize, struct passwd** result);
+struct passwd*	getpwuid(uid_t uid);
+int				getpwuid_r(uid_t uid, struct passwd* pwd, char* buffer, size_t bufsize, struct passwd** result);
+void			setpwent(void);
+
+__END_DECLS
+
+#endif