math: Use erfcf from CORE-MATH

math: Use erfcf from CORE-MATH

The CORE-MATH implementation is correctly rounded (for any rounding mode)
and shows better performance to the generic erfcf.

The code was adapted to glibc style and to use the definition of
math_config.h.

Benchtest on x64_64 (Ryzen 9 5900X, gcc 14.2.1), aarch64 (M1,
gcc 13.2.1), and powerpc (POWER10, gcc 13.2.1):

latency                       master       patched  improvement
x86_64                       98.8796       66.2142       33.04%
x86_64v2                     98.9617       67.4221       31.87%
x86_64v3                     87.4161       53.1754       39.17%
aarch64                      33.8336       22.0781       34.75%
power10                      21.1750       13.5864       35.84%
powerpc                      21.4694       13.8149       35.65%

reciprocal-throughput         master       patched  improvement
x86_64                       48.5620       27.6731       43.01%
x86_64v2                     47.9497       28.3804       40.81%
x86_64v3                     42.0255       18.1355       56.85%
aarch64                      24.3938       13.4041       45.05%
power10                      10.4919        6.1881       41.02%
powerpc                       11.763       6.76468       42.49%

Signed-off-by: Alexei Sibidanov <sibid@uvic.ca>
Signed-off-by: Paul Zimmermann <Paul.Zimmermann@inria.fr>
Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: DJ Delorie <dj@redhat.com>