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/ftw.h

@@ -0,0 +1,36 @@
+#ifndef _FTW_H
+#define _FTW_H 1
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/ftw.h.html
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#include <sys/stat.h>
+
+struct FTW
+{
+	int base;
+	int level;
+};
+
+#define FTW_F	1
+#define FTW_D	2
+#define FTW_DNR	3
+#define FTW_DP	4
+#define FTW_NS	5
+#define FTW_SL	6
+#define FTW_SLN	7
+
+#define FTW_PHYS	1
+#define FTW_MOUNT	2
+#define FTW_DEPTH	3
+#define FTW_CHDIR	4
+
+int ftw(const char* path, int (*fn)(const char*, const struct stat* ptr, int flag), int ndirs);
+int nftw(const char* path, int (*fn)(const char*, const struct stat*, int, struct FTW*), int fd_limit, int flags);
+
+__END_DECLS
+
+#endif