- if only the module itself is documented (e.g. `trac_mimeview`) and no
.rst files for submodules are present, we include the re-exported symbols
as well (this was the behavior so far for `__init__.py` files)
- when submodules are also documented (e.g. `trac_util.rst` and the various
`trac_util_*.rst` files), we only consider the symbols defined in
`__init__.py`, as for a normal module
