Drop references to inaccessible types

[reitzig]

Say I have a setup similar to this:

internal protocol Foo {}
public  protocol Bar

public struct FooBar: Foo, Bar {}

I do not want the documentation of FooBar to reference Foo unless --min-acl is set accordingly. Currently, Jazzy just copies (?) the declaration line (but does not link Foo since no documentation is created for that protocol).

[reitzig]

Related: #768, #777

[reitzig]

Some care has to be taken:

public  protocol Bar {}
internal protocol Foo: Bar {}

public struct FooBar: Foo {}

We want to see struct FooBar: Bar in the documentation.