dir.c: git-status --ignored: don't list empty directories as ignored

dir.c: git-status --ignored: don't list empty directories as ignored

'git-status --ignored' lists empty untracked directories as ignored, even
though they don't have any ignored files.

When checking if a directory is already listed as untracked (i.e. shouldn't
be listed as ignored as well), don't assume that the directory has only
ignored files if it doesn't have untracked files, as the directory may be
empty.

Signed-off-by: Karsten Blees <redacted>
Signed-off-by: Junio C Hamano <redacted>