List PEAR packages from all registered channels

This trivial patch allows the PEAR package regular expression matcher to catch packages from all registered PEAR channels. I encountered this as an issue when trying to track the installation of Horde packages (http://www.horde.org/), which were mysteriously missing. Turns out that blueprint only issues a `pear list` which captures only the default channel at pear.php.net. To get all registered channels for PEAR packages, we need `pear list -a`.