BUG: Fixed an issue where .pyi files were ignored by numpy sub-packages

[BvB93]

As of the moment .pyi stub files are only recognized for the main numpy namespace and the numpy.core sub-package,
despite the existence of stub files in other sub-packages such as numpy.lib and numpy.random.

This PR fixes aforementioned issue.

[charris]

Out of curiosity, how is this all supposed to work? I had the impression that all the information would be available at the top level.

[BvB93]

Out of curiosity, how is this all supposed to work? I had the impression that all the information would be available at the top level.

This is mostly (though not exclusively) relevant for sub-module that do not export their content to the main numpy namespace (e.g. numpy.random). Stubs for the latter are currently not picked up as "*.pyi" is missing from the setups data_files entry.

[charris]

Thanks Bas.