When building packet-dap.c on an empty build tree, packet-dap.c would

When building packet-dap.c on an empty build tree, packet-dap.c would
be incorrect on the first pass and only be correct when remade.
The reason was that disp-exp.cnf was created incorrectly on first pass.
disp-exp.cnf required dop-exp.cnf to build correctly, so add a mechanism
to add dependencies for export files.

Note: Only the cmake change has been tested, the autofoo stuff requires
  testing.

svn path=/trunk/; revision=52120