[patch, fortran] Some corrections for DO loop index warnings

[Steve Kargl]

On Mon, Aug 12, 2019 at 05:18:18PM +0200, Thomas Koenig wrote:
> Hello world,
> 
> the attached patch fixes three problems with DO loop index warnings:
> 
> - DO loops in contained procedures were not checked
> 
> - Zero-trip loops gave a false positive
> 
> - DO loops in blocks gave the same warning twice
> 
> plus it fixes the resulting fallout from the test suite.
> 
> Regression-tested.  OK for trunk?  I also think that this is something
> that could be safely backported to gcc-9.
> 

Ok.  If it regression cleanly on gcc9, go ahead an commit there as well.

-- 
Steve