WL#2269 Enable query cache for NDB part 2

-This is mostly fixes for correct behaviour when using query cache + transactions + the thread that
fetches commit count from NDB at regular intervals. The major fix is to add a
list in thd_ndb, that keeps a list of NDB_SHARE's that were modified by
transaction and then "clearing" them in ndbcluster_commit.

sql/ha_ndbcluster.h

@@ -60,6 +60,7 @@ typedef struct st_ndbcluster_share {
   pthread_mutex_t mutex;
   char *table_name;
   uint table_name_length,use_count;
+  uint commit_count_lock;
   ulonglong commit_count;
 } NDB_SHARE;
 
@@ -77,6 +78,7 @@ class Thd_ndb {
   NdbTransaction *all;
   NdbTransaction *stmt;
   int error;
+  List<NDB_SHARE> changed_tables;
 };
 
 class ha_ndbcluster: public handler
@@ -226,7 +228,7 @@ class ha_ndbcluster: public handler
   char *update_table_comment(const char * comment);
 
  private:
-  int check_ndb_connection();
+  int check_ndb_connection(THD* thd= current_thd);
 
   NdbTransaction *m_active_trans;
   NdbScanOperation *m_active_cursor;
@@ -250,6 +252,7 @@ class ha_ndbcluster: public handler
   ha_rows m_rows_to_insert;
   ha_rows m_rows_inserted;
   ha_rows m_bulk_insert_rows;
+  ha_rows m_rows_changed;
   bool m_bulk_insert_not_flushed;
   ha_rows m_ops_pending;
   bool m_skip_auto_increment;

sql/set_var.cc

@@ -413,7 +413,8 @@ sys_var_thd_bool
 sys_ndb_use_exact_count("ndb_use_exact_count", &SV::ndb_use_exact_count);
 sys_var_thd_bool
 sys_ndb_use_transactions("ndb_use_transactions", &SV::ndb_use_transactions);
-sys_var_long_ptr sys_ndb_cache_check_time("ndb_cache_check_time", &ndb_cache_check_time);
+sys_var_long_ptr
+sys_ndb_cache_check_time("ndb_cache_check_time", &ndb_cache_check_time);
 #endif
 
 /* Time/date/datetime formats */
@@ -686,10 +687,10 @@ sys_var *sys_variables[]=
 #endif  
 #ifdef HAVE_NDBCLUSTER_DB
   &sys_ndb_autoincrement_prefetch_sz,
+  &sys_ndb_cache_check_time,
   &sys_ndb_force_send,
   &sys_ndb_use_exact_count,
   &sys_ndb_use_transactions,
-  &sys_ndb_cache_check_time,
 #endif
   &sys_unique_checks,
   &sys_updatable_views_with_limit,
@@ -1276,7 +1277,6 @@ static int check_max_delayed_threads(THD *thd, set_var *var)
   return 0;
 }
 
-
 static void fix_max_connections(THD *thd, enum_var_type type)
 {
 #ifndef EMBEDDED_LIBRARY