reordered Item_row class variables to be sorted by memory size

fixed layout

fixed bug of calling setup_fields without correct lex->current_select pointer in mysql_derived
more correct creation of reference in Item_field::fix_field

removed unused items

Changed timestamp to return string in YYYY-MM-DD HH:MM:SS format.
DATE_ADD() and related functions now returns correct DATE/DATETIME type depending on argument types.
Now all tests passes, still some work left to remove warnings in log files from mysql-test-run

Class for sending data from server to client (Protocol)
This handles both the old ( <= 4.0 ) protocol and then new binary protocol that is used for prepared statements.

NULL fixed
max_length fixed
layout fixed

  Fix for save_in_field to take extra bool argumnet (4.0 merge compatibility)

optimization of left expression evaluation
more descriptive method name

Optimized SELECT DISTINCT ... ORDER BY ... LIMIT
Fixed reference to uninitalized variable

ORDER clause, where table is one of union'ed tables.

after merge fix

fixed sunction-test select in IN bug
fixed unions in subselect bug

more efficient reference creation
fixed table_name of Field in temporary table

Fixed context in error mesages

prevent using references on sum function (except HAVING clouse of current select) and forward references