vcols in the table definition are intentionaly bad and produce
warnings when a table is opened. In some cases (depending on the
TDC/TC state as left by earlier tests) a table might be opened in the
middle of the test, resulting in spurious warnings. Suppress them.
Also, don't run main.mdev-504 for ps-protocol at all (instead of
disabling ps-protocol inside the test, but still running the test)
It was used for get_datetime_value() and for thd->is_error().
But in fact, get_datetime_value() never used thd argument, because the
cache ptr argument was NULL. And thd->is_error() check was not needed
at that place at all.
it used current_thd->alloc() and allocated on the thd's execution arena,
not on table->expr_arena.
Remove THD::arena_for_cached_items that is temporarily set in
update_virtual_fields(), and replaces THD arena in get_datetime_value().
Instead set THD arena to table->expr_arena for the whole duration
of update_virtual_fields()
Item_func_le included Arg_comparator. Arg_comparator remembered
the current_thd during fix_fields and used that value during
execution to allocate Item_cache in get_datetime_value().
But for vcols fix_fields and val_int can happen in different threads.
Same bug for Item_func_in using in_datetime or cmp_item_datetime,
both also remembered current_thd at fix_fields() to use it later
for get_datetime_value().
As a fix, these objects no longer remember the current_thd,
and get_datetime_value() uses current_thd at run time. This
should not increase the number of current_thd calls much, as
Item_cache is created only once anyway.
