Description:
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Sometimes it would be very useful to have a PDO::quoteIdentifier($name) method
for the same reasons there already is a PDO::quote($name) method i.e. because the quoting characters might be different among database engines and to prevent SQL-Injection-Attacks.

Implementing it shouldn't be hard as the lower level DB engines provide a corresponding function or if not, the ANSI SQL quoting character could be used as fall-back.