I've simplified the Darwin/Mac OS X startup script I submitted earlier

I've simplified the Darwin/Mac OS X startup script I submitted earlier
in the year. This version has only the two files required by the Darwin
startup bundle design. Plus the sh script now uses Darwin-standard
functions to start up PostgreSQL, and it checks for the presence of a
variable in /etc/hostconfig, as do other Darwin startup scripts.

I suggest that a new directory be created,
contrib/start-scripts/darwin, and that these two files be put into it.
Folks who want to use the script can read the comments inside it to
figure out how to use it.

David Wheeler