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
diff --git a/libc/dns/net/getnameinfo.c b/libc/dns/net/getnameinfo.c
index d6c4488..f940109 100644
--- a/libc/dns/net/getnameinfo.c
+++ b/libc/dns/net/getnameinfo.c
@@ -61,7 +61,7 @@
 #include <assert.h>
 #include <limits.h>
 #include <netdb.h>
-#include "arpa_nameser.h"
+#include <arpa/nameser.h>
 #include "resolv_private.h"
 #include <sys/system_properties.h>
 #include <stdlib.h>