[Openal] User Installation Instructions

[Garin Hiebert]

One (small) additional comment -- for the Windows installer, you can  
run it from your installer with the "/s" option and it will do a non- 
interactive ("silent") install for you.  It will update an existing  
installation if an old installation is found, will leave the existing  
installation alone if it is down-rev, or do a new install if necessary.

Garin