* autogen.sh: Support addition of external modules via `GRUB_CONTRIB' variable. * Makefile.in: Likewise.
* autogen.sh: Add a call to `gendistlist.sh'.
This prevents autoheader from being rerun by make if somebody changes configure.ac or aclocal.m4 and runs autogen.sh. Suggested by Christian Franke <Christian.Franke@t-online.de>