[fortran,patch] Don't write common more than once in a module file (PR 30285)

[Tobias Schlüter]

Tobias Schlüter wrote:
> The updated patch looks ok.

Sorry, that I didn't think of this earlier.  If you haven't committed 
the patch yet, and since you're touching it, can you please change the 
code to traverse the common tree in left-to-right order in order to 
prevent spurious differences between module files?  Note that there's an 
early return in write_common0, so you have to be a bit careful.

Thanks,
- Tobi