COLUMNS

ANALYSIS:
=========
A valgrind error is reported when CREATE TABLE .. SELECT
involving BIT columns triggers a column type redefinition.

In general the pack_flag is set for BIT columns in
'mysql_prepare_create_table()'. However, during the above
operation, redefined column types was handled after the
special handling for BIT columns and thus pack_flag ended
up not being set correctly triggering the valgrind error.

FIX:
====
The patch fixes this problem by setting pack_flag correctly
for BIT columns in the case of column type redefinition.