How to grow the Fortran I/O parameter struct and keep ABI compatibility

[FX Coudert]

> Suggestion:  We should make sure we can accommodate F2003 with
> 4.2 and 4.3 by increasing the possible number of flags as needed.

I'm in favour of that, and I already started writing the necessary  
patch. But it looks like we'll have to bump the so number a last  
time, for 4.3, and then make the private part of the structure wider,  
to accomodate any new flags (for things like extension, or the way  
we'll really handle asynchronous I/O).

FX