global symbols are regularly extracted even if not included by include-symbols

[mizvekov]

For an example such as:

include/test.hpp:

struct Baz {};

mrdocs.yml:

verbose: true
source-root: .
input:
  - include
file-patterns:
  - '*.hpp'
include-symbols:
  - 'mrdocs::**'
multipage: false
generator: xml

The following XML is produced:

<mrdocs>
<namespace id="//////////////////////////8=">
  <struct name="Baz" id="+/u4DxnodNEFBQQP6NiTfrWbM64=">
    <file short-path="include/test.hpp" source-path="include/test.hpp" line="1" class="def"/>
  </struct>
</namespace>
</mrdocs>

Where it can be seen Baz is extracted.