faster exp10f code

[paul zimmermann]

       Hi,

the 3 patches referenced below implement some faster exp10f code, inspired by
the expf code, that is much faster than the current one (tested on x86_64).
Here are the "make bench" results (I had to add an entry for exp10f):

before new code:
  "exp10f": {
   "": {
    "duration": 3.40525e+09,
    "iterations": 6.4368e+07,
    "max": 65906.3,
    "min": 24.056,
    "mean": 52.9029
   }

with new code:
  "exp10f": {
   "": {
    "duration": 3.30806e+09,
    "iterations": 1.59728e+08,
    "max": 39557.8,
    "min": 16.104,
    "mean": 20.7106
   }

I disabled the code in math/w_exp10f_compat.c by adding #if 0 ... #endif
around it, since I don't know how to properly do it.

Paul Zimmermann

[1] https://homepages.loria.fr/PZimmermann/glibc-contrib/0001-added-new-code-for-exp10f-inspired-from-expf-and-reu.patch
[2] https://homepages.loria.fr/PZimmermann/glibc-contrib/0002-e_exp10f.c-cleaned-up-added-error-analysis-and-comme.patch
[3] https://homepages.loria.fr/PZimmermann/glibc-contrib/0003-integrate-new-exp10f-code.patch