lo-pack-sources: use the same top-level directory in all tarballs
lo-pack-sources: use the same top-level directory in all tarballs

It allows to avoid symlinks more easily.

In addition, I did some clean up. I removed support for packing pieces
from standalone checkout. I guess that noone is using it.

Change-Id: I3c712f5eb12108229a157c636e0a63eca4ae0d6b

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core