to allow temp table operations):

  - Move opening of temporary tables (in normal case) to the stage of
    statement execution which precedes privilege checking. In the upcoming
    patches we will use this fact during privilege checks to easily and
    cheaply determine if table is temporary;

  - make open_table() to work with base tables and views only.
    It will be renamed to open_base_table_or_view()
    in a follow-up patch.

  - introduce open_temporary_table() to open temporary tables
    (similar to open_table());

  - introduce open_temporary_tables() to open temporary tables
    corresponding to table list elements;

  - introduce a new "command flag" (CF_PREOPEN_TMP_TABLES) to mark
    statements that work with temporary tables, thus temporary tables
    should be opened for those statements;

  - open temporary tables in a unified way in the beginning of
    the statements marked with CF_PREOPEN_TMP_TABLES flag;

  - introduce a new "command flag" (CF_HA_CLOSE) to mark statements
    for which open handlers (by HANDLER OPEN) should be closed;

  - close open handlers in a unified way in the beginning of
    the statements marked with CF_HA_CLOSE flag.