Moved nameser.h and namser_compat.h to public include dir

This is part of the upstream sync (Net/Open/Free BSDs expose the
nameser.h in their public headers).

Change-Id: Ib063d4e50586748cc70201a8296cd90d2e48bbcf

libc/dns/gethnamaddr.c

@@ -59,7 +59,7 @@
 #include <sys/un.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
-#include "arpa_nameser.h"
+#include <arpa/nameser.h>
 #include "resolv_private.h"
 #include "resolv_cache.h"
 #include <assert.h>