Bug#19660 mysqldump --single-transaction should be with CONSISTENT SNAPSHOT

client/mysqldump.c:
  Bug#19660 mysqldump --single-transaction should be with CONSISTENT SNAPSHOT
  
  - Remove old BEGIN syntax and replace with START TRANSATION. Add CONSISTENT SNAPSHOT option for servers that support it.

client/mysqldump.c

@@ -2407,7 +2407,7 @@ static int do_reset_master(MYSQL *mysql_con)
 }
 
 
-static int start_transaction(MYSQL *mysql_con, my_bool consistent_read_now)
+static int start_transaction(MYSQL *mysql_con)
 {
   /*
     We use BEGIN for old servers. --single-transaction --master-data will fail
@@ -2422,10 +2422,8 @@ static int start_transaction(MYSQL *mysql_con, my_bool consistent_read_now)
                                         "SET SESSION TRANSACTION ISOLATION "
                                         "LEVEL REPEATABLE READ") ||
           mysql_query_with_error_report(mysql_con, 0,
-                                        consistent_read_now ?
                                         "START TRANSACTION "
-                                        "WITH CONSISTENT SNAPSHOT" :
-                                        "BEGIN"));
+                                        "/*!40100 WITH CONSISTENT SNAPSHOT */"));
 }
 
 
@@ -2652,7 +2650,7 @@ int main(int argc, char **argv)
   if ((opt_lock_all_tables || opt_master_data) &&
       do_flush_tables_read_lock(sock))
     goto err;
-  if (opt_single_transaction && start_transaction(sock, test(opt_master_data)))
+  if (opt_single_transaction && start_transaction(sock))
       goto err;
   if (opt_delete_master_logs && do_reset_master(sock))
     goto err;