- Adding variable m_cached_result_type to keep the variable type consistent
  during the execution of a statement.
- Before each result set is returned to the client the description of each
  column is sent as meta data.
  Previously the result type for a column could change if the hash variable
  entry changed between statements. This caused the result set of the query
  to alternate column types in certain cases which is not supported by MySQL
  client-server protocol. Example:
  Previously this sequence:
    SET @A:=1;
    SELECT @A:="text", @A;
  would return "text", "text";
 
  After the change the SELECT returns "text", 0
  The reson for this is that previously the result set from 'SELECT @A;'
  would always be of the type STRING, whereas now the type of the variable
  is taken from the last SET statement. However, 'SELECT @A:="text"' will
  return type of STRING since the right side of the assignment is used.


mysql-test/r/ps_2myisam.result:
  Changed test result because SQL type of a user variable now
  more accurately represents its Item type: since Item type of a variable
  can be either STRING, INT, DECIMAL or DOUBLE, SQL type of the
  result set metadata now can be either MYSQL_TYPE_VARCHAR,
  MYSQL_TYPE_LONGLONG, MYSQL_TYPE_NEWDECIMAL or MYSQL_TYPE_DOUBLE.
  
  Previously it was always MYSQL_TYPE_VARCHAR.
  
  In particular, integer variables now have changed from
  MYSQL_TYPE_VARCHAR to MYSQL_TYPE_LONGLONG.
mysql-test/r/ps_3innodb.result:
  Changed test result because SQL type of a user variable now
  more accurately represents its Item type: since Item type of a variable
  can be either STRING, INT, DECIMAL or DOUBLE, SQL type of the
  result set metadata now can be either MYSQL_TYPE_VARCHAR,
  MYSQL_TYPE_LONGLONG, MYSQL_TYPE_NEWDECIMAL or MYSQL_TYPE_DOUBLE.
  
  Previously it was always MYSQL_TYPE_VARCHAR.
  
  In particular, integer variables now have changed from
  MYSQL_TYPE_VARCHAR to MYSQL_TYPE_LONGLONG.
mysql-test/r/ps_4heap.result:
  Changed test result because SQL type of a user variable now
  more accurately represents its Item type: since Item type of a variable
  can be either STRING, INT, DECIMAL or DOUBLE, SQL type of the
  result set metadata now can be either MYSQL_TYPE_VARCHAR,
  MYSQL_TYPE_LONGLONG, MYSQL_TYPE_NEWDECIMAL or MYSQL_TYPE_DOUBLE.
  
  Previously it was always MYSQL_TYPE_VARCHAR.
  
  In particular, integer variables now have changed from
  MYSQL_TYPE_VARCHAR to MYSQL_TYPE_LONGLONG.
mysql-test/r/ps_5merge.result:
  Changed test result because SQL type of a user variable now
  more accurately represents its Item type: since Item type of a variable
  can be either STRING, INT, DECIMAL or DOUBLE, SQL type of the
  result set metadata now can be either MYSQL_TYPE_VARCHAR,
  MYSQL_TYPE_LONGLONG, MYSQL_TYPE_NEWDECIMAL or MYSQL_TYPE_DOUBLE.
  
  Previously it was always MYSQL_TYPE_VARCHAR.
  
  In particular, integer variables now have changed from
  MYSQL_TYPE_VARCHAR to MYSQL_TYPE_LONGLONG.
mysql-test/r/ps_7ndb.result:
  Changed test result because SQL type of a user variable now
  more accurately represents its Item type: since Item type of a variable
  can be either STRING, INT, DECIMAL or DOUBLE, SQL type of the
  result set metadata now can be either MYSQL_TYPE_VARCHAR,
  MYSQL_TYPE_LONGLONG, MYSQL_TYPE_NEWDECIMAL or MYSQL_TYPE_DOUBLE.
  
  Previously it was always MYSQL_TYPE_VARCHAR.
  
  In particular, integer variables now have changed from
  MYSQL_TYPE_VARCHAR to MYSQL_TYPE_LONGLONG.
mysql-test/r/sp-vars.result:
  Added test case. Previously variables could change their variable type during 
  the execution of a statement.
  Which variable type to use in the statement is specified in
  any previous statement.
mysql-test/r/type_date.result:
  This test case result is changed because it is no longer allowed for user
  variables to change their variable type during the execution of a statement.
  The determination of which variable type to use in the statement is specified in
  any previous statement.
mysql-test/r/user_var.result:
  This test case result is changed because it is no longer allowed for user
  variables to change their variable type during the execution of a statement.
  The determination of which variable type to use in the statement is specified in
  any previous statement.
mysql-test/t/sp-vars.test:
  Added test case. Previously variables could change their variable type during 
  the execution of a statement.
  Which variable type to use in the statement is specified in
  any previous statement.
mysql-test/t/type_date.test:
  This test case result is changed because it is no longer allowed for user
  variables to change their variable type during the execution of a statement.
  The determination of which variable type to use in the statement is specified in
  any previous statement.
sql/item_func.cc:
  Adding variable m_cached_result_type to keep the variable type consistent
  during the execution of a statement.
  Previously the result type could change if the hash variable entry changed
  between statements. This caused the result set of the query to alternate
  column types in certain cases.
sql/item_func.h:
  Adding variable m_cached_result_type to keep the variable type consistent
  during the execution of a statement.
  Previously the result type could change if the hash variable entry changed
  between statements. This caused the result set of the query to alternate
  column types in certain cases.