Fix encoding issues and added missing "pages" key

There are some issues with char encoding from the geo-ip plugins. By
forcing utf8 it seems to be working better. There where also a missing
label value «pages» for «OS» and «BROWSER» causing the Browser and OS
tab not to work.

Tested with: AWSTATS DATA FILE 7.2 (build 1.992) + plugins: geoip,
geoip_city_maxmind