Updated earthdistance/cube patches

Since the diffs from Satuday night.
I changed earthdistance not to build cube automatically. I changed both
cube and earthdistance to grant execute to public functions being created.
These diffs are versus today's cvs.

The cube diff changes create function to create or replace function and
has some minor documentation changes.

The earthdistance diff changes adds a set of functions for handling
distances on teh surface of the earth based on the contrib/cube package.
The new functions are all of language type 'sql'. I also fixed a couple
of bugs in the old earthdistance function based on the point datatype.
I added documentation for the new functions and put in a regression
test set for both the new and old functions.