sql/sql_lex.cc:
  tabllist creation routine moved to SELECT_LEX_UNION class & made recursive
sql/sql_lex.h:
  list creation routine moved to SELECT_LEX_UNION class
sql/sql_parse.cc:
  list creation routine moved to SELECT_LEX_UNION class
  anonymous union used for storing TABLE*/TABLE_LIST*
sql/sql_union.cc:
  anonymous union used for storing TABLE*/TABLE_LIST*
sql/table.h:
  anonymous union used for storing TABLE*/TABLE_LIST*