Bug 7902 - Adding Function to Check for Existence of Tables

Bug 7902 - Adding Function to Check for Existence of Tables

This patch adds a function TableExists which checks for the existence
of a given table and returns 1 or 0 accordingly. This allows us to
check for the existence of a given table when doing operations on
tables which may not exist in a given database which, in turn, will
reduce the number of red errors which show up after an upgrade.

An example of its use is included in this patch.

Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>