BY A CONCURRENT TRANSACTIO

The member function QUICK_RANGE_SELECT::init_ror_merged_scan() performs
a table handler clone. Innodb does not provide a clone operation.  
The ha_innobase::clone() is not there. The handler::clone() does not 
take care of the ha_innobase->prebuilt->select_lock_type.  Because of 
this what happens is that for one index we do a locking read, and 
for the other index we were doing a non-locking (consistent) read. 
The patch introduces ha_innobase::clone() member function.  
It is implemented similar to ha_myisam::clone().  It calls the 
base class handler::clone() and then does any additional operation 
required.  I am setting the ha_innobase->prebuilt->select_lock_type 
correctly. 

rb://1060 approved by Marko