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.
clamav: update 0.98.5 bottle.