[libc] add various macros relate to *ADDR* (llvm#164830)

This patch adds 4 macros in the `netinet/in.h` header, as specified by
POSIX standards.

Author: c8ef

libc/include/llvm-libc-macros/netinet-in-macros.h

@@ -9,6 +9,9 @@
 #ifndef LLVM_LIBC_MACROS_NETINET_IN_MACROS_H
 #define LLVM_LIBC_MACROS_NETINET_IN_MACROS_H
 
+#include "../llvm-libc-types/in_addr_t.h"
+#include "__llvm-libc-common.h"
+
 #define IPPROTO_IP 0
 #define IPPROTO_ICMP 1
 #define IPPROTO_TCP 6
@@ -24,4 +27,10 @@
 #define IPV6_LEAVE_GROUP 21
 #define IPV6_V6ONLY 26
 
+#define INADDR_ANY __LLVM_LIBC_CAST(static_cast, in_addr_t, 0x00000000)
+#define INADDR_BROADCAST __LLVM_LIBC_CAST(static_cast, in_addr_t, 0xffffffff)
+
+#define INET_ADDRSTRLEN 16
+#define INET6_ADDRSTRLEN 46
+
 #endif // LLVM_LIBC_MACROS_NETINET_IN_MACROS_H