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/un.h

@@ -0,0 +1,20 @@
+#ifndef _SYS_UN_H
+#define _SYS_UN_H 1
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_un.h.html
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#include <bits/types/sa_family_t.h>
+
+struct sockaddr_un
+{
+	sa_family_t	sun_family;				/* Address family. */
+	char		sun_path[FILENAME_MAX];	/* Socket pathname. */
+};
+
+__END_DECLS
+
+#endif