Add hints for PDO functions

Hey,
I don't know if this is done right but I wanted to add support for PDO functions as I need those sometimes. So I took all but "__construct" form here: http://php.net/manual/de/book.pdo.php

I know this won't work right now, but I saw that you splitted those functions in the develop branch so I did the same for the PDO functions.

Just tell me if something is wrong :)

Greets,
Dominic