Enhancement request: enable manylinux builds

[brosenfi]

As of this writing I believe gopy does not support manylinux builds due to the fact that it requires libpython (libpython*.so) to be present. Manylinux builds are against static Python (see https://github.com/pypa/manylinux/issues/255 and https://github.com/pypa/manylinux/issues/30 for details). Can gopy be enhanced to build modules against static Python instead of the current libpython setup? I will look into a contribution for this if one of the regular maintainers thinks that it's feasible.