HISTORY updated, 7.3 branded

OK, the HISTORY file is updated, and 7.3 is branded and ready for beta1.

I used the same HISTORY categories Peter made in 7.2.  I liked them.

Please review the HISTORY file.  I am sure there are improvements that
can be made.

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
359-1001+  If your life is a hard drive,     |  13 Roberts Road +  Christ can be your backup.        |  Newtown Square,
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