The CORE-MATH implementation is correctly rounded (for any rounding mode).
This can be checked by exhaustive tests in a few minutes since there are
less than 2^32 values to check against for example GNU MPFR.
This patch also adds some bench values for tgammaf.

Tested on x86_64 and x86 (cfarm26).

With the initial GNU libc code it gave on an Intel(R) Core(TM) i7-8700:

      "tgammaf": {
       "": {
        "duration": 3.50188e+09,
        "iterations": 2e+07,
        "max": 602.891,
        "min": 65.1415,
        "mean": 175.094
       }
      }

With the new code:

      "tgammaf": {
       "": {
        "duration": 3.30825e+09,
        "iterations": 5e+07,
        "max": 211.592,
        "min": 32.0325,
        "mean": 66.1649
       }
      }

With the initial GNU libc code it gave on cfarm26 (i686):

  "tgammaf": {
   "": {
    "duration": 3.70505e+09,
    "iterations": 6e+06,
    "max": 2420.23,
    "min": 243.154,
    "mean": 617.509
   }
  }

With the new code:

  "tgammaf": {
   "": {
    "duration": 3.24497e+09,
    "iterations": 1.8e+07,
    "max": 1238.15,
    "min": 101.155,
    "mean": 180.276
   }
  }

Signed-off-by: Alexei Sibidanov <sibid@uvic.ca>
Signed-off-by: Paul Zimmermann <Paul.Zimmermann@inria.fr>

Changes in v2:
    - include <math.h> (fix the linknamespace failures)
    - restored original benchtests/strcoll-inputs/filelist#en_US.UTF-8 file
    - restored original wrapper code (math/w_tgammaf_compat.c),
      except for the dealing with the sign
    - removed the tgammaf/float entries in all libm-test-ulps files
    - address other comments from Joseph Myers
      (https://sourceware.org/pipermail/libc-alpha/2024-July/158736.html

)

Changes in v3:
    - pass NULL argument for signgam from w_tgammaf_compat.c
    - use of math_narrow_eval
    - added more comments

Changes in v4:
    - initialize local_signgam to 0 in math/w_tgamma_template.c
    - replace sysdeps/ieee754/dbl-64/gamma_productf.c by dummy file

Changes in v5:
    - do not mention local_signgam any more in math/w_tgammaf_compat.c
    - initialize local_signgam to 1 instead of 0 in w_tgamma_template.c
      and added comment

Changes in v6:
    - pass NULL as 2nd argument of __ieee754_gammaf_r in
      w_tgammaf_compat.c, and check for NULL in e_gammaf_r.c

Changes in v7:
    - added Signed-off-by line for Alexei Sibidanov (author of the code)

Changes in v8:
    - added Signed-off-by line for Paul Zimmermann (submitted of the patch)

Changes in v9:
    - address comments from review by Adhemerval Zanella
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>