mrdocs produces bogus diagnostic when inheriting from an external class

[mizvekov]

Reduced test case from recent #1077 failure:

namespace ns {
  struct Foo {
    /// bar
    int bar();
  };
}
/// Baz
struct Baz : ns::Foo {};

Assumes mrdocs.yml includes some other namespace, but doesn't include ns:

include-symbols:
  - 'mrdocs::**'

For this test case, mrdocs produces the following diagnostic:

test.hpp:4:5:
    1) Baz::bar: Missing documentation for return value
  4 |     int bar();
    |     ^~~~~~~~~~

The documentation for bar produces a diagnostic even though it is external to the project (member of an excluded namespace).

[mizvekov]

This also produces the following XML:

<namespace id="//////////////////////////8=">
  <struct name="Baz" id="+/u4DxnodNEFBQQP6NiTfrWbM64=">
    <file short-path="1119.cpp" source-path="1119.cpp" line="8" class="def"/>
    <base>
      <type id="CjJeLCME/Qvw46zQD//BJMQ4nB4=" name="ns::Foo"/>
    </base>
    <doc>
      <brief>
        <text>Baz</text>
      </brief>
    </doc>
    <function name="bar" id="I/ezlBucwKKyfOJy2BdJDHM4sDc=">
      <file short-path="1119.cpp" source-path="1119.cpp" line="4"/>
      <return>
        <type name="int"/>
      </return>
      <doc>
        <brief>
          <text>bar</text>
        </brief>
      </doc>
    </function>
  </struct>
</namespace>
</mrdocs>

It also doesn't look right that we document bar as being a member of Foo.

[alandefreitas]

Two valid problems here:

• Baz should have been extracted regardless of the base class issue
• There should be no warnings regarding the base class if one is included and the other is excluded (and only included later on via inherit-base-members)