add rsyslog version fact support for Gentoo

lib/facter/rsyslog_version.rb

@@ -31,6 +31,14 @@ Facter.add(:rsyslog_version) do
             else
               nil
             end
+        when "Gentoo"
+            command='equery -q -C list -F \'$version\' rsyslog'
+            version = Facter::Util::Resolution.exec(command)
+            if version =~ /^(.+)$/
+                $1
+            else
+                nil
+            end
         else
             nil
         end