[Bug libfortran/65563] Segfault on reopening fort.xxx file with explicit name

[tkoenig at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65563

--- Comment #7 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
I upgraded to recent trunk (which I hadn't done for some time) and found that I
can no longer reproduce the error with 5.0.

So I'll make this into a test case and commit this as obvious, to make sure no
regressions come up.