!CURSOR->INDEX->IS_COMMITTED()

PROBLEM:

On 5.7 & trunk:
When trying to do a simple DML like REPLACE , server used to crash with
error : ROW_NOT_FOUND
on update . The issue is basically the value of max_prefix(which is the
maximum value of prefix
for the index) being incorrectly set. When the index uses whole of the
column length , the
max_prefix value was not being set to 0(since max_prefix=0 would
represent indexing the whole column).
Hence causing the length of column being wrongly set  and to the
discrepancy as we try to fetch the
row while doing a REPLACE.

FIX:

Fix is to set the max_prefix to 0 if a column is a part of an index
where the prefix length is 0
and otherwise set it to any higher values (based on non zero prefix
length for field).

Reviewed by:Jimmy Yang<Jimmy.Yang@oracle.com>
Reviewed by:Thirunarayanan Balathandayuth
	    <thirunarayanan.balathandayuth@oracle.com>
Rb :12375