New MAC OUI capabilities

I've committed changes to the main tree which update the pg_proc system
catalog, so initdb is required.

As discussed recently, I've added some contrib/mac/ routines to support
generating a table, macoui, which contains current manufacturers'
identification fields for hardware MAC addresses. I've made a few other
changes, including dropping the macaddr_manuf() built-in function.

Note that I did *not* add a current copy of the oui.txt file from IEEE,
since it is over half a meg uncompressed. But we could add it to cvs if
it is advisable.

The contrib/mac directory does not yet have a README, but should.

More details below...
                    - Thomas

The CVS log:

Add functions to convert to and from text, and to truncate to MAC OUI.
Remove hardcoded macaddr_manuf(), which had really old, obsolete info.Replace this with some contrib/mac/ code to
maniagOUI info from IEEE.