Update pg_config.h.win32 for beta?

Should src/include/pg_config.h.win32 contain a beta/devel marker?  I
thought it used to, but I don't see one now.  I thought it was suppose
to match pg_config.h's PG_VERSION.

--  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,
Pennsylvania19073