MXS-1475 Address review issues

- Clean up session header.
- Add test case

include/maxscale/session.h

@@ -154,6 +154,8 @@ typedef struct session_variable
 } SESSION_VARIABLE;
 
 typedef std::tr1::unordered_map<std::string, SESSION_VARIABLE> SessionVarsByName;
+#else
+typedef void SessionVarsByName;
 #endif
 
 /**
@@ -190,11 +192,7 @@ typedef struct session
         const struct server *target; /**< Where the statement was sent */
     } stmt;  /**< Current statement being executed */
     bool qualifies_for_pooling; /**< Whether this session qualifies for the connection pool */
-#ifdef __cplusplus
     SessionVarsByName*      variables;        /*< @maxscale variables associated with this session */
-#else
-    void*                   variables;
-#endif
     skygw_chk_t             ses_chk_tail;
 } MXS_SESSION;
 

server/modules/protocol/MySQL/mariadbclient/test/test_setparser.cc

@@ -218,6 +218,12 @@ struct TEST_CASE
         "@MAXSCALE.CACHE.ENABLED",
         "TRUE"
     },
+    {
+        "SET @MAXSCALE.CACHE.ENABLED = TRUE, @maxscale.cache.enabled = FALSE",
+        P::IS_SET_MAXSCALE,
+        "@maxscale.cache.enabled",
+        "FALSE"
+    },
 };
 
 const int N_TEST_CASES = sizeof(test_cases) / sizeof(test_cases[0]);