.gitignore: Ignore a couple more files

Ignore autotools artifacts in the root directory too, so that even an
in-tree build will leave git status reasonably clean.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Get rid of autoreconf -i warnings

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
configure.ac: Add missing things noticed by autoscan

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>