[LIBM] Introduce faster method for evaluating polynomials (#239)

This patch replaces Horner method which was used to evaluate polynomials with Estrin's method( https://en.wikipedia.org/wiki/Estrin%27s_scheme ) that allows more parallel computations with out-of-order execution.
This patch also introducing a new reduction method to tan.
With this patch, mainly computation for double-precision functions becomes faster, and the effect is like a few percent to 20 percent. For example, the ratio between execution time of the following functions before and after applying this patch is shown below.

Sleef_atan2d4_u35 : 1.21
Sleef_powd4_u10 : 1.17
Sleef_sind4_u35 : 1.10
Sleef_tand4_u10 : 1.04
Sleef_tand4_u35 : 1.17