[Patch, fortran] PR31193 - ICE on non-constant character transfer

[François-Xavier Coudert]

> Bootstrapped and regtested on Cygwin_NT/amd64 - OK for trunk and,
> eventually, 4.2?

The patch is OK. I couldn't apply it and test however, so please
update your tree (if need be) and double-check everything before
commiting.

For 4.2, I think we should follow the procedure and not backport it
(unless it's a regression, but I don't think so). We have enough work
on mainline

Thanks for the work,
FX