removed "of is null" if it is possible
  (this cset should be SCRUM related, but not approved as scrum task yet)


mysql-test/r/subselect.result:
  new subselect test result (new place of error detecting & and more subselect reducing)
sql/item.cc:
  layout fix
sql/item.h:
  unneed ';'
  fixed print pethod
sql/item_cmpfunc.cc:
  new method to support transformation after fix_fields
sql/item_cmpfunc.h:
  new method to support transformation after fix_fields
  fixed Item printing
sql/item_subselect.cc:
  new transformation
sql/item_subselect.h:
  new transformation
sql/sql_derived.cc:
  'table' & 'table_list' now is not union
sql/sql_lex.cc:
  'table' & 'table_list' now is not union to support reinit only shared tables (but all)
sql/sql_lex.h:
  mark fake st_select_lex
sql/sql_olap.cc:
  fixed table assignment
  TODO added
sql/sql_select.cc:
  'table' & 'table_list' now is not union
  transforming subselect
sql/sql_union.cc:
  prepare make on fix_fields
sql/sql_yacc.yy:
  fixed layout
sql/table.h:
  'table & 'table_list' now is different fields