Add '.empty' files to empty directories so
 hg and git create them on check-out.
(grafted from 333a9f5ba5f268ca99bc2eaf933a1169b20df010)

--HG--
extra : source : 333a9f5ba5f268ca99bc2eaf933a1169b20df010
Merge pull request #13 from ehuelsmann/1.4

Add '.empty' files to empty directories so