Generate pow lookup tables with higher precision
Generate pow lookup tables with higher precision

possibly due to glibc-2.29 commit 424c4f60ed6190e2ea0e72e0873bf3ebcbbf5448
pow is using fused-multiply-add (fma) if available.
That caused the fluidsynth binaries to differ depending on
the build machine's CPU.

This was visible among others in
grep '7.58577575029183[56]e-04' fluidsynth-2.0.3/build/fluid_conv_tables.c

See https://reproducible-builds.org/ for why this is matters.

Closes #512.

FluidSynth/fluidsynth,FluidSynth/fluidsynth,FluidSynth/fluidsynth,FluidSynth/fluidsynth