when we open the HEAP table for the first time since server restart,
in hp_open(), we set a flag to propagate this info to the handler level
which then writes a DELETE FROM this_heap_table to the binlog.
It is not a perfect solution for the bug, because between the server start and
the first open of the table, the slave still had old data in his table so
a SELECT on the slave may show wrong content. But if there is a --init-file
to populate the HEAP table on master as startup, then this is a safe fix
(I'll put a note about init-file in the HEAP section of the manual).
