reduce minimum required version for automake to 1.9

since ubuntu 8.04LTS had 1.10, I was not able to test it. The BWGrid
cluster has 1.9 and it seems to work. Thank goes to Lena for catching
this!

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@7836 2fb0f335-1f38-0410-981e-8018bf24f1b0