basic: Add our own <netinet/in.h> and <net/if.h> headers

These glibc headers conflicts with the corresponding linux headers
(<linux/in.h> and <linux/if.h>) and impose an include order (the glibc one
has to be included before any linux header is included). This makes sorting
includes a royal pain so let's define our own versions of these headers using
various linux headers to do all the work and filling in the missing bits
ourselves.

src/basic/include/net/if.h

@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <linux/if.h>
+
+#define IF_NAMESIZE       16
+
+extern unsigned int if_nametoindex(const char *__ifname) __THROW;
+extern char *if_indextoname(unsigned int __ifindex, char __ifname[IF_NAMESIZE]) __THROW;

src/basic/include/netinet/in.h

@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <linux/in.h>
+#include <linux/in6.h>
+#include <linux/ipv6.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <sys/socket.h>
+
+#define INET_ADDRSTRLEN 16
+#define INET6_ADDRSTRLEN 46
+
+extern const struct in6_addr in6addr_any;        /* :: */
+extern const struct in6_addr in6addr_loopback;   /* ::1 */
+#define IN6ADDR_ANY_INIT { { { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 } } }
+#define IN6ADDR_LOOPBACK_INIT { { { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1 } } }
+
+typedef uint32_t in_addr_t;