work on linux distros especially ones which return package numbers

stated in issue #246. here are the same examples

Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.0.5) Gecko/2008121911 CentOS/3.0.5-1.el5.centos Firefox/3.0.5
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.8) Gecko/20100723 SUSE/3.6.8-0.1.1 Firefox/3.6.8
Mozilla/5.0 (X11; U; Linux x86_64; en; rv:1.9.0.8) Gecko/20080528 Fedora/2.24.3-4.fc10 Epiphany/2.22 Firefox/3.0
Mozilla/5.0 (X11; U; Linux x86_64; nl; rv:1.9.1.11) Gecko/20100714 openSUSE/3.0.6 Thunderbird/3.0.6 ThunderBrowse/3.3.2
Mozilla/5.0 (X11; U; Linux x86_64; en-US) AppleWebKit/534.16 SUSE/10.0.626.0 (KHTML, like Gecko) Chrome/10.0.626.0 Safari/534.16