The `ifaddrs` interface is available since api version 24 in android.
The function signatures are now equal to the standard Linux function
signatures.

    - Copy 17 functions definitions from src/unix/mod.rs
      to src/unix/bsd/mod.rs src/unix/haiku/mod.rs
      src/unix/notbsd/linux/mod.rs and src/unix/solaris/mod.rs
    - Add some functions to android that was cfged out
    - Remove cf* and tc* functions implementations for android
      (they are available with api >= 12, which was release in 2011)

- some tests are failing
- remove readlink, timegm and sig* functions in favor of the
  unix/mod.rs definitions
- remove time64_t (it is not defined for aarch64)
- move some definitions to android/b32.rs and create appropriated
  definitions in android/b64.rs

Sadly, the sysinfo struct varies slightly between Musl and Glibc / Bionic.

This means that users need to be careful when using the uptime, and should
always cast it to a signed value. Why uptime can be signed is beyond me...