Bison license exception

[Sandro Mani]

Hi

While reviewing mingw-cfitsio, we encountered the situation of bison 
parser sources [1][2] containing the following:

/* [... standard GPLv3+ header ...] */

/* As a special exception, you may create a larger work that contains
    part or all of the Bison parser skeleton and distribute that work
    under terms of your choice, so long as that work isn't itself a
    parser generator using the skeleton or a modified version thereof
    as a parser skeleton.  Alternatively, if you modify or redistribute
    the parser skeleton itself, you may (at your option) remove this
    special exception, which will cause the skeleton and the resulting
    Bison output files to be licensed under the GNU General Public
    License without this special exception.

    This special exception was added by the Free Software Foundation in
    version 2.2 of Bison.  */

cfitsio is licensed MIT. Is my understanding correct that this special 
exception means that these files are also MIT licensed, being 
distributed as part of cfitsio, and hence that the license field of the 
package only needs to specify MIT?

Thanks
Sandro

[1] https://github.com/healpy/cfitsio/blob/master/eval_y.c
[2] https://github.com/healpy/cfitsio/blob/master/eval_tab.h