Fix endianness bug when generating fingerprint in big endian machines

[pranavkaruvally]

Fixes https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1093700

The script

import acoustid

example_file = '/usr/share/sounds/freedesktop/stereo/alarm-clock-elapsed.oga'
print(acoustid.fingerprint_file(example_file)[1].decode())

generates wrong fingerprint in big endian machines.

This PR fixes this issue.