Robustness of MusicExtractor descriptor values across platforms

[dbogdanov]

This is an umbrella issue for all robustness-related issues for MusicExtractor used in AcousticBrainz:

• AudioLoader updates: Numerical changes in descriptors values due to AudioLoader updates #401
• Difference between architectures: different results for 32 bit builds (and minor differences between runs) #179, this should be further expanded by testing difference between x86, x86-64, ARM, etc. TODO: decide which platforms to test.