Add libevent

Author: joanhey

frameworks/PHP/reactphp/benchmark_config.json

@@ -17,7 +17,7 @@
       "webserver": "None",
       "os": "Linux",
       "database_os": "Linux",
-      "display_name": "reactphp",
+      "display_name": "reactphp [libevent]",
       "notes": "",
       "versus": "php"
     },