[Dune] m4 cleanup

[Christian Engwer]

Hi,

> indeed I forgot that $() are bash- and ksh-only. The problem w/
> backticks is that they're special in m4.
> 
>   `this is quoted in m4'
> 
> As a result, considering e.g.
> 
>   dune_griddim.m4:42 variable_griddim="$``(``GRIDDIM``)``"
> 
> autom4te refuses to even continue parsing that file:
> 
> $ autom4te dune_griddim.m4
> /usr/bin/m4:dune_griddim.m4:42: ERROR: end of file in string
> autom4te-2.64: /usr/bin/m4 failed with exit status: 1

But none of the files in dune-common did have this kind of problem,
did they?

Look at pkg.m4 for example. They are using the same syntax.

Christian