JOINING TABLES, VIEWS
ISSUE         : 1. Offset address from a join buffer of size 
                   >=4gb can be >4 bytes long. But we 
                   have only considered offsets upto 4bytes long.
                   This will lead to invalid buffer read and 
                   memory corruption henceforth.
                2. If we fail to allocate join buffer then
                   we are not freeing the JOIN_CACHE_X instance.
                   Now next join buffer will wrongly take this
                   unfreed JOIN_CACHE_X instance as its previous
                   cache. Hence in incremental join buffer 
                   implementation there will be a chance for 
                   unallocated memory access.
Solution      : 1. Now for join buffer >=4gb we have made offest
                   address size = 8 bytes.
                2. If we fail to allocate the join buffer we free
                   the JOIN_CACHE_X instance also.