[Pkg-postgresql-public] postgresql-common ported to Homebrew

[Peter Eisentraut]

Just for your entertainment, I had a moment of "homesickness" and ported
the postgresql-common package to Homebrew/OS X.  It basically works, you
can use pg_wrapper for the clients and pg_createcluster etc. for the
server.

I haven't tried to run the test suite, but I plan to.

You can see the differences here:
https://github.com/petere/postgresql-common/compare/master...homebrew

Most of it has to do with different installation paths.  There are some
OS-specific incompatibilities with ps and ldd.  I also had to duplicate
a lot of the build instructions that are embedded in debian/rules.