clamav 0.98.5

* Version bump. 
* Fixed head.
* New recommend dependency *(It’s actually an old recommended dependency that we haven’t been building).* 
* Moves the sysconf dir to a directory inside HOMEBREW_PREFIX/etc to make it a little tidier.
* Adds some caveats to explain clamav’s confusing error messages on initial run.
* Adds a test.
If we wanted to put in place workable defaults, curling or borrowing Apple's defaults [here](https://www.opensource.apple.com/source/clamav/clamav-158/clamav.Conf/clamd.conf.default) and then adjusting the paths to fit our expected format would be the best bet, IMO.