Add a top level makefile to make common tasks easier. Supported targets:
make - build modules
make install - install modules (honors DESTDIR)
make clean - clean up
make tarballs - create source tarballs from current HEAD
Note: "make tarballs" uses "git archive" so that it only works in a local
copy of the git repository, not in a directory created by unpacking
a tarball.
Add *.tar to .gitignore to hide tarballs created by "make tarballs".
Michal Kubecek