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.
It generates two files along the lines of ``` clamd.conf.sample ``` and stashes them in ``` #{etc}/clamav ``` at the moment. I'll refine the caveat to make it slightly less confusing.