Removing "brik" from release script

[Mark Mitchell]

I think that it's time to remove the generation of the "brik" files
from the release script.  These checksum files aren't really necessary
at a time where (a) communication links are generally error-free, and
(b) we're generating md5sum files for the release tarballs.  The use
of "brik" is just one more thing to complicate the release generation.

I'll remove the use of "brik" after the 3.4.0 release unless people
object.

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com