deps,http: llhttp set max header size to 8KB

CVE-2018-12121

As per nodejs-private/node-private#149 for http_parse but for llhttp

Ref: nodejs-private/node-private#143
PR-URL: nodejs-private/node-private#149
Reviewed-By: Matteo Collina <hello@matteocollina.com>

Author: rvagg

src/node_http_parser.cc

@@ -852,7 +852,7 @@ class Parser : public AsyncWrap, public StreamListener {
 
   static const parser_settings_t settings;
 #ifdef NODE_EXPERIMENTAL_HTTP
-  static const uint64_t kMaxHeaderSize = 80 * 1024;
+  static const uint64_t kMaxHeaderSize = 8 * 1024;
 #endif  /* NODE_EXPERIMENTAL_HTTP */
 };