THRIFT-727 - C++: what() method of generated exceptions will provide more information

Patch: Anna Dymek <aadymek@gmail.com>
Client: C++

This closes #469
diff --git a/tutorial/cpp/CppServer.cpp b/tutorial/cpp/CppServer.cpp
index 84b79d4..6b22193 100644
--- a/tutorial/cpp/CppServer.cpp
+++ b/tutorial/cpp/CppServer.cpp
@@ -71,7 +71,7 @@
     case Operation::DIVIDE:
       if (work.num2 == 0) {
         InvalidOperation io;
-        io.what = work.op;
+        io.whatOp = work.op;
         io.why = "Cannot divide by 0";
         throw io;
       }
@@ -79,7 +79,7 @@
       break;
     default:
       InvalidOperation io;
-      io.what = work.op;
+      io.whatOp = work.op;
       io.why = "Invalid Operation";
       throw io;
     }