INSERT...ON DUPLICATE KEY UPDATE may cause error 1032: 
"Can't find record in ..." if we are inserting into
InnoDB table unique index of partial key with
underlying UTF-8 string field.

This error occurs because INSERT...ON DUPLICATE uses a wrong
procedure to copy string fields of multi-byte character sets
for index search.


mysql-test/t/innodb_mysql.test:
  Added test case for bug #13191.
mysql-test/r/innodb_mysql.result:
  Added test case for bug #13191.
sql/field.h:
  Fixed bug #13191.
  Field_string::get_key_image() virtual function was overloaded
  to implement copying of variable length character (UTF-8) fields.
  Field::get_key_image() function prototype has been changed to
  return byte size of copied data.
sql/field.cc:
  Fixed bug #13191.
  Field_string::get_key_image() virtual function was overloaded
  to implement copying of variable length character (UTF-8) fields.
  Field::get_key_image() function prototype has been changed to
  return byte size of copied data.
sql/key.cc:
  Fixed bug #13191.
  INSERT...ON DUPLICATE KEY UPDATE may cause error 1032: 
  "Can't find record in ...".
  This error occurs because INSERT...ON DUPLICATE uses
  a wrong procedure to copy field parts for index search.
  key_copy() function has been fixed.