[patch, fortran] Some cleanup / fixes in front-end statement walker

[Thomas Koenig]

Steven Bosscher wote:
>> This patch corrects these things.  Regression-tested.
>> OK for trunk?  (I will not be able to commit for a few
>> days due to business travel, unless somebody is _really_
>> fast :-)
>
> Looks OK to me. Fast enough for you?

Yes indeed.  Committed as rev. 180063.

Thanks a lot!

	Thomas