new user interface to reduce_angs_with_amplitude
new user interface to reduce_angs_with_amplitude

if NOT defined, the functionality is not used.
if DEFINED, the functionality is used:
- reduce_angs_with_amplitude<0: default value is used (0.3);
- any other value of reduce_angs_with_amplitude will be used, without much
  protection on it.

SixTrack/SixDesk,SixTrack/SixDesk,SixTrack/SixDesk,SixTrack/SixDesk