If found a few times the need to download a single, uncompressed file
which needs to be patched. The available fetch methods do not appear
to be appropriate. So, I've added the function
'uncompressed-file-fetch'. This and the function
'broken-tarball-fetch' which currently resides in 'engineering.scm'
should probably belong to '(guix build utils)'.

Regards,
Fede