Upgrading from 4.4.2 to 4.5.0 and getting a new error that I've not noticed in the forum

Fatal error: Call to undefined function: db_encode_blob() in /home/ ... /includes/bootstrap.inc on line 147

I see the line in bootstrap.inc but don't understand the 'call to undefined function' portion, esp. how to explore whether the function is defined or not, how to define the function ...

Any help or insight would be helpful.
Thanks,
Jeff