[Dune] m4 cleanup

[Sven Marnach]

Hi Christian,

Christian Engwer schrieb am Fr, 11. Sep 2009, um 13:55:34 +0200:
> $() is a bashism and `` is posix-sh.

you are wrong with this one:

    http://opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_06_03

$() _is_ POSIX and is generally considered to be the better solution.
It is much more flexible -- for example it can be nested, which is
impossible with ``.  There are other advantages as well, but I forgot
what exactly they are.

Greetings,
    Sven