git ls files recursively show ignored files

Make git-ls-files --others --ignored recurse into non-excluded
subdirectories.

Typically when asking git-ls-files to display all files which are
ignored by one or more exclude patterns one would want it to recurse
into subdirectories which are not themselves excluded to see if
there are any excluded files contained within those subdirectories.

Signed-off-by: Junio C Hamano <junkio@cox.net>