Updating the length of a custom field does not result in the log table field length being updated

If a custom field is 3 char long & it gets changed to 10 char long the civicrm_value_xx table is alted to accomodated this - but not log_civicrm_value_xx table - which means saves of the longer value can result in a fatal error & transaction rollback.

The code for coping with table changes explicitly says is only responds on add & not change - I'm unsure why & in testing this usecase it worked fine. The comment predates git & it may be that the reason has been resolved since the comment was written