Issue 8716 - Top-level module should have package access to itself

http://d.puremagic.com/issues/show_bug.cgi?id=8716

A top-level module such as `module foo;` should have access to its own symbols if they're declared as having package access. This didn't work before as the implementation expected to always find a `parent` of a module which is a package, but top-level modules don't have packages.