Row::at() now uses the ColData ctor with an explicit length parameter when creating the object it returns.  This fixes yet another place where we can be bit by query results containing nulls.  Probably isn't the last one, though.
Row::at() now uses the ColData ctor with an explicit length parameter
when creating the object it returns.  This fixes yet another place where
we can be bit by query results containing nulls.  Probably isn't the
last one, though.

winsock/mysqlpp,winsock/mysqlpp,winsock/mysqlpp