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

Ref: https://android.googlesource.com/platform/bionic/+/1c19194c9d2518dbe86973cd313a277ecb70d75c%5E%21/libc/include/sys/sysconf.h

Was able to move some of them up one level so they are valid on more
platforms with less duplication

Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>

Note that termios2 doesn't exist on powerpc(64), termios
is used instead.

* Add syscall tables to most remaining arches in `src/unix/notbsd`
* Add aarch64/arm musl to CI
* Update dependencies

Rebase of #610 and also move emscripten up much higher in the hierarchy to
ensure that it doesn't have too much of a ripple effect on other platforms.

This involved moving down a good number of definitions, but hopefully was done
with care to not break anything!

For some reason, they are in the NDK sources but
they are not available in the tests. I don't know what
Android does here, but nothing that makes sense.

I'd rather avoid the duplication, this is discussed in #707.