THRIFT-2888: JSON generator - fixed missing include

Client: JSON
Patch: Pascal Bach

<limits> was used but not directly included
diff --git a/compiler/cpp/src/generate/t_json_generator.cc b/compiler/cpp/src/generate/t_json_generator.cc
index 1cb8584..154a64d 100644
--- a/compiler/cpp/src/generate/t_json_generator.cc
+++ b/compiler/cpp/src/generate/t_json_generator.cc
@@ -24,10 +24,12 @@
 #include <fstream>
 #include <iostream>
 #include <sstream>
+#include <limits>
 
 #include <stdlib.h>
 #include <sys/stat.h>
 #include <sstream>
+
 #include "t_generator.h"
 #include "platform.h"