[Patch, fortran] PR31160 - %VAL and related features need to be documented.

[Paul Thomas]

Gerald,
>
> I am happy to see documentation fixes and enhancements backported to 
> release branches, with a single constraint: documentation of later 
> releases should be better than those of earlier ones. :-)
>
>   
My fellow gfortran maintainers have shamed me into this - to the extent 
of raising a PR on it:)

Should I degrade the entry for 4.2, to be consistent with your suggested 
approach?  I could remove all adjectives and adverbs...

Paul