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/net/if.h

@@ -0,0 +1,46 @@
+#ifndef _NET_IF_H
+#define _NET_IF_H 1
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/net_if.h.html
+
+#include <sys/cdefs.h>
+
+#include <sys/socket.h>
+
+#define IF_NAMESIZE 16
+
+__BEGIN_DECLS
+
+struct if_nameindex
+{
+	unsigned if_index;	/* Numeric index of the interface. */
+	char* if_name;		/* Null-terminated name of the interface. */
+};
+
+struct ifreq
+{
+	union {
+		struct sockaddr ifru_addr;
+		struct sockaddr ifru_netmask;
+		struct sockaddr ifru_gwaddr;
+		struct sockaddr ifru_hwaddr;
+		unsigned char __min_storage[sizeof(sockaddr) + 6];
+	} ifr_ifru;
+};
+
+#define SIOCGIFADDR		1	/* Get interface address */
+#define SIOCSIFADDR		2	/* Set interface address */
+#define SIOCGIFNETMASK	3	/* Get network mask */
+#define SIOCSIFNETMASK	4	/* Set network mask */
+#define SIOCGIFGWADDR	5	/* Get gateway address */
+#define SIOCSIFGWADDR	6	/* Set gateway address */
+#define SIOCGIFHWADDR	7	/* Get hardware address */
+
+void					if_freenameindex(struct if_nameindex* ptr);
+char*					if_indextoname(unsigned ifindex, char* ifname);
+struct if_nameindex*	if_nameindex(void);
+unsigned				if_nametoindex(const char* ifname);
+
+__END_DECLS
+
+#endif