Source file defining global variables for configuration paths. This

Source file defining global variables for configuration paths.  This
has two purposes:

 - If ./configure is re-run to configure Samba for a new set of path
   or prefix, then when Samba is re-built it really will use the new
   paths.

 - This is a step towards making sure all programs can be consistently
   told to use a different configuration file or prefix directory,
   which is required for testing.  Possibly not true at the moment.
(This used to be commit f54c64babd31abf9f5bbf960316d4b9502b9477d)