[sane-devel] add a Canon scanner to scanbuttond

[Thomas Rechberger]

> i run scanbuttond -f again but still shows nothing.
> Maybe its not that easy as i thought?
>
>

not having much clue of C but it seems that scanbuttond reads which 
backend libsane is using. Because this scanner doesnt use plustek 
backend i will then try to create a new canon630u backend in scanbuttond.

My Scanner is reported as:
canon630u:libusb:002:006