query_classifier.cc: added detection for CREATE TEMPORARY TABLE and setting a new query type QUERY_TYPE_CREATE_TMP_TABLE for it.

query_classifier.h: added QUERY_TYPE_CREATE_TMP_TABLE and QUERY_TYPE_READ_TMP_TABLE for use of temporary table support.
hashtable.c:Added variant of hashtable which is 'flat', that is, stored to existing memory instead of allocating memory as a part of the call. Existing function declarations don't change but added hashtable_alloc_flat for the purpose. Both hashtable_alloc and hashtable_alloc_flat now call the real allocation function, hashtable_alloc_real. hashtable_free only frees memory which is allocated in hashtable_alloc_real.
hashtable.h: added a flag to HASHTABLE struct to indicate whether hashtable owns its memory or not.
readwritesplit.h: Added RSES_PROP_TYPE_TMPTABLES property type to be used for keeping the hashtable for tablenames.
readwritesplit.c: Added comments about temporary table support implementation.

server/include/hashtable.h

@@ -84,12 +84,17 @@ typedef struct hashtable {
 	SPINLOCK	spin;				/**< Internal spinlock for the hashtable */
 	int		n_readers;			/**< Number of clients reading the table */
 	int		writelock;			/**< The table is locked by a writer */
+	bool            ht_isflat;			/**< Indicates whether hashtable is in stack or heap */
 #if defined(SS_DEBUG)
         skygw_chk_t     ht_chk_tail;
 #endif
 } HASHTABLE;
 
 extern HASHTABLE	*hashtable_alloc(int, int (*hashfn)(), int (*cmpfn)());
+HASHTABLE		*hashtable_alloc_flat(HASHTABLE* target, 
+						int size,
+						int (*hashfn)(),
+						int (*cmpfn)());
 				/**< Allocate a hashtable */
 extern void		hashtable_memory_fns(HASHTABLE *, HASHMEMORYFN, HASHMEMORYFN, HASHMEMORYFN, HASHMEMORYFN);
 				/**< Provide an interface to control key/value memory