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/nameser/ns_ttl.c b/libc/dns/nameser/ns_ttl.c
index cc98331..1ad3b49 100644
--- a/libc/dns/nameser/ns_ttl.c
+++ b/libc/dns/nameser/ns_ttl.c
@@ -28,7 +28,7 @@
 
 /* Import. */
 
-#include "arpa_nameser.h"
+#include <arpa/nameser.h>
 
 #include <ctype.h>
 #include <errno.h>