Depending on the mercurial or tar version installed, the generated tar
file can be different. We change the test to check the checksum of the
files included in the tarball instead of the tar file.

Also add the sha512 and sha512file template functions.

We also add tests to `test.pl` to check that we exit with an error when
sha256sum or sha512sum is wrong (and that we don't when it's the
expected one).