extensions generated without namespaces, name clashes ignored

[gsnoff]

Example

When I execute protoc supplied with the plugin on those files, only the extension with name 'foobar' in package 'foo.bar.baz' gets registered in generated autoload.php. The extension with the same name in package 'foo.bar' is missing at all.

For comparison, when protoc generates c++/java/python code, both of these extensions are present in the corresponding namespaces/packages/modules.