The $Id$ keywords were used in Subversion where they can be substituted
with filename, last revision number change, last changed date, and last
user who changed it.
In Git this functionality is different and can be done with Git attribute
ident. These need to be defined manually for each file in the
.gitattributes file and are afterwards replaced with 40-character
hexadecimal blob object name which is based only on the particular file
contents.
This patch simplifies handling of $Id$ keywords by removing them since
they are not used anymore.
Allow drivers to add methods to dbh and stmt objects
(note that we can't use a class, because the use only sees the PDO class).
Clarify the api slightly:
PDO::exec() is used for one-shot queries that don't return rows
PDO::query() is a convenience function for returning a rowset without
having to go through the steps of preparing and executing.