I removed the SANE patches (well actually I just hid them).
For some time now, the testtool package contains the 'patch-sane.sh' script, that patches the sane-backend sources. Therefore a separate SANE patch is more or less redundant.
To patch SANE now do the following:
1) Download and unpack the testtool and sane-backends source packages
2) Go to the testtool directory and patch sane-backends:
(substitute the proper sane-backend directory)
3) Go to the sane-backend directory and build sane-backends:
I think it is a good idea to first try the testtool before trying to make SANE work.