GMP and clang bugginess

[Torbjörn Granlund]

I added clang 3.5 and clang 3.6 testing to a Breadwell system.
We got one new build failure, and a handful new check  failures.

I suspect the "steamroller" failures are a real hardware compatibility
problem.

I suspect the build failure is due to plain (Intel NUC) hardware without
ECC, or Linux bugs,

That would make this Debian/Ubuntu version of clang 3.6 usable for
x86-64.  I am not sure this is a patched version, or if it has been
patgched and repatched (meaning that an earlier Debian/Ubuntu clang 3.6
was less usable).  If we're attempting to have whitelists/blacklists, we
need to understand that type of issues.

-- 
Torbjörn
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