64-bit PowerPC Altivec support

[Wolfgang Bangerth]

>> Segher mentioned that this patch fixes a couple PRs.  Can the PRs be
>> closed, and mentioned in the ChangeLog?
>
>If we mention the PRs in the Changelog, the Bugzilla maintainers will
>see them, test again, and close the bug.  At least that's how I think
>it works.

No. We _may_ see them, but in general we can't test them except on the most 
widely available platforms. powerpc64-unknown-linux-gnualtivec is certainly 
not one of them. Mentioning a PR in the ChangeLog is only useful since it 
adds this ChangeLog entry to the audit trail of the PR, adding a cross-link 
so to say.

Please close the PRs yourself. Otherwise we end up with lots of PRs for which 
something was committed half a year ago and nobody knows any more whether 
that fixed the PR or not. Also, what's the purpose of having someone else 
testing again if you already know that the bug is fixed.

Thanks
  Wolfgang
 
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Wolfgang Bangerth              email:            bangerth@ices.utexas.edu
                               www: http://www.ices.utexas.edu/~bangerth/