Upstream GYP has been unmaintained for some time now. The only big
downstream user is Node.js and they already maintain GYP build files
for their other dependencies.

This commit removes vcbuild.bat because:

1. it's entirely built around GYP, and
2. duplicates a lot of functionality that cmake provides out of the box

This commit also removes appveyor.yml. It hasn't been used after we
stopped providing prebuilt binaries for Windows about two years ago.

As if that isn't enough, this commit also removes the Android build
scripts. They were wrappers around GYP. Use CMake.

PR-URL: https://github.com/libuv/libuv/pull/2682
Refs: https://github.com/libuv/libuv/pull/2681


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>