remove the hook for creating the m4 directory

remove the hook for creating the m4 directory

Now that we do not override the automagic handling of include
directories witbh aclocal, the missing m4 directories will be
automatically created by aclocal itself.

So we can drop of hooks.

Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
[yann.morin.1998@free.fr: slight rewording in the commit log]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>