Mostly just tidy up, catching pages that I missed the first time round.
A small number of pages were given a bit more reformat. A bit beyond
the remit of this merge request but not too much has been changed.
Thomas Soumarmon <soumarmt@nerim.net>. Changed to use sanei_usb instead of
direct /dev/usb/scanner access. Added manual page. Fixed some portablility
issues and some warnings. Added SANE headers.