libc: Add missing declarations in <netinet/in.h>

Add missing declarations:
  INET_ADDRSTRLEN
  IN6_IS_ADDR_MC_NODELOCAL
  IN6_IS_ADDR_MC_GLOBAL

It has been reported that these prevent compilation of the Boost libraries
with the NDK. The corresponding patch has already been performed under
development/ndk/platforms/android-3/include.

Change-Id: I4ac514973daf3c06a8ef5538d7df79142a98e562

libc/include/netinet/in.h

@@ -38,6 +38,8 @@ __BEGIN_DECLS
 
 #define IPPORT_RESERVED  1024
 
+#define INET_ADDRSTRLEN 16
+
 extern int bindresvport (int sd, struct sockaddr_in *sin);
 
 static const struct in6_addr in6addr_any = IN6ADDR_ANY_INIT;