Issue/Cause:
Issue is of memory corruption.During optimization phase, pattern to be matched in where 
clause, is prepared. This is done in Item_func_concat::val_str() function which forms the
resultant string (tmp_value) and return its pointer. In caller, Item_func_like::fix_fields, 
pattern is made to point to this string (tmp_value). In further processing, tmp_value is 
getting modified which causes pattern to have changed/wrong values.

Fix:
Allocate its own memroy location in caller, copy value of resultant string (tmp_value) 
into that and make pattern to point to that. This makes sure no further changes to 
tmp_value will affect pattern.