fix inaccuracy of j0f for x >= 2^127 when sin(x)+cos(x) is tiny (v3)

[Florian Weimer]

* Paul Zimmermann:

>        Dear Adhemerval,
>
> thank you again for your useful comments.
>
>> Does it require any ULP adjustment (at least on the architecture you
>> tested it)?
>
> I reset to 0 the j0/float values in sysdeps/x86_64/fpu/libm-test-ulps,
> then ran "make regen-ulps", and got:
>
> $ diff ../sysdeps/x86_64/fpu/libm-test-ulps /localdisk/zimmerma/glibc/build/math/NewUlps
> 1315c1315
> < float: 0
> ---
>> float: 8
> 1321c1321
> < float: 0
> ---
>> float: 4
> 1327c1327
> < float: 0
> ---
>> float: 5
> 1333c1333
> < float: 0
> ---
>> float: 5
>
> which were the original values except for j0_towardzero (it was 6).
> However the same applies to "master", so this is independent from my change.
> Anyway, I decreased the value from 6 to 5.

I suggest to leave it at 6, other CPU variants may still need the 6
there.

Thanks,
Florian