[#30192] Disallow directory listings in default config

This is a continuation of [JoomlaCode item 30192](http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=30192) and modifies the distributed `htaccess.txt` and `web.config.txt` files to disallow directory listings by default.
The name of the function sounds wrong having `eaccelerator` in the name.
But I think com_postinstall allows to show messages without any action anyway. So the function is probably not needed anyway.