mysql-test/t/merge.test:
  additional test
sql/item.h:
  parameter to detect need of saving view field names
sql/item_subselect.cc:
  arena fix
  used nearest thd pointer
sql/item_sum.cc:
  after merge fix
sql/mysql_priv.h:
  after merge fix
sql/sql_base.cc:
  fixed unique test
  fixed postmerge arena mamgement
sql/sql_class.h:
  mey method to detect conventional execution
sql/sql_handler.cc:
  new parameter
sql/sql_lex.cc:
  fixed postmerge arena mamgement
sql/sql_parse.cc:
  fixed unique test
sql/sql_select.cc:
  fixed postmerge arena mamgement
sql/sql_union.cc:
  fixed postmerge arena mamgement
sql/sql_view.cc:
  fixed postmerge arena mamgement
sql/table.cc:
  fixed postmerge arena mamgement