Also generate overrides

[dcodeIO]

This PR changes the way tsd-jsdoc checks for members already declared on the parent. Instead of searching for an already existing member with the same name on any parent, it now checks if the member is actually inherited, so that explicitly overridden members (i.e. a method that has a different signature) are generated.

This might affect other projects using tsd-jsdoc, depending on how overrides are documented there. If, for example, an @override annotation is present, then the member will still be skipped with the PR applied, but if it is not explicitly annotated as one, the member will now be generated. This is a bit counter-intuitive but it seems to be the jsdoc-way (it discards any jsdoc on the child when it sees @override, just like @inheritdoc does - see)

See: #9

[englercj]

As mentioned in #9, v2 supports this behavior but it is currently broken in jsdoc.