fix warning about fortran_src raised at build

[ndarmage]

Hi,

I noticed the following warning at build: WARNING: The config value fortran_src' has type list', defaults to `str'.

Please, change the line (setup function in fortran_autodoc module): app.add_config_value('fortran_src', '.', False) to: app.add_config_value('fortran_src', ['.'], False)

.. note:: I cannot commit/push - sorry.

Thanks in advance. Regards.