bug#35374: Calc; Div by 0 in solving system

[Christopher Howard]

I am now using Emacs 26.2 (through Guix) but am able to reproduce the
original error in 26.2. I patched just this function (math-try-solve-
for) and reloaded it. The error went away, and the correct solution was 
generated.

I did not try running the tests.

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Christopher Howard
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On Sun, 2019-09-22 at 19:34 +0200, Mattias Engdegård wrote:
> tags 35374 patch
> stop
> 
> > Maybe someone more knowledgeable about Calc can help further.
> 
> Much to our surprise, very few people volunteered their service. Now,
> despite being grossly under-qualified for the task, I did give it a
> go. After all, we can't have it fail on simple linear equation
> systems now can we.
> 
> Please try this patch.
>