* Split `FLAC__cpu_info` into CPU specific functions. We now have
  `ia32_cpi_info` and `x86_64_cpu_info` and a simple obvious way
  to add support for other CPUs.
* Improve handling of Android OS.
* Remove more #ifdefs where possible.
* Compile (syntax and type check) DEBUG output code even when debugging
  is disabled.
* Remove build support for ancient NetBSD version 1.5 (version 1.6 was
  released in 2002).