[PATCH] math: Add more inputs to atan2 accuracy tests [BZ #28765]

[Paul Zimmermann]

       Dear Sunil,

first, with your atan2 patch fixing BZ #28765, I cannot get errors larger than
4 ulps with the SSE4.2 code. The largest error I get so far is 2.39063 ulps
with 0x1.a11891ec004d4p-348,0x1.814830510be26p-348.

> --- a/sysdeps/x86_64/fpu/libm-test-ulps
> +++ b/sysdeps/x86_64/fpu/libm-test-ulps
> @@ -214,10 +214,10 @@ double: 1
>  float: 2
>  
>  Function: "atan2_vlen4_avx2":
> -double: 1
> +double: 2

I wonder whether this should be increased to 3, since I get an error of 3.46942
ulps for the following inputs and AVX2 (and that inputs should be
added to math/auto-libm-test-in): 0x1.a83f842ef3f73p-633,0x1.a799d8a6677ep-633

>  Function: "atan2_vlen8":
> -double: 1
> +double: 2
>  float: 2
>  
>  Function: "atan2_vlen8_avx2":

Best regards,
Paul