Improved Joomla! extensions update handling of paid for extensions to Joomla 2.5.x  

Similar to recent feature proposal for the 3.x branch (https://github.com/joomla/joomla-cms/pull/2769), here is a proposal to allow the Joomla! updater to process paid-for extensions updates, that may require various types of credentials to be passed along the file download process.

This is implemented by simply firing an event, so the changes are minimal, about 4 lines added to one file. Extensions maybe implement event handler to append credentials to the download urls or add authorization request headers as they see fit.

A sample plugin for extensions using the Akeeba Release system is attached to the Joomlacode tracker item below,a s it can't be attached here.

Joomlacode feature tracker item: http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33133&start=0