Whatever happened to res_mysql.conf?
It’s my understanding that it was changed to "res_config_mysql.conf"
but neither file is included in the distro.
Is it required for FreePBX or only for a2billing?
At this time, FreePBX doesn’t use this. However this is used if your are running the Apple Raisin Asterisk branch , which you can find more information about setting up at http://www.freepbx.org/trac/wiki/appleraisinmysql.