Remove useless code that propagated FrontendProtocol to a backend via a

PostgresMain switch.  In point of fact, FrontendProtocol is already set
in a backend process, since ProcessStartupPacket() is executed inside
the backend --- it hasn't been run by the postmaster for many years.
And if it were, we'd still certainly want FrontendProtocol to be set before
we get as far as PostgresMain, so that startup errors get reported in the
right protocol.

-v might have some future use in standalone backends, so I didn't go so
far as to remove the switch outright.

Also, initialize FrontendProtocol to 0 not PG_PROTOCOL_LATEST.  The only
likely result of presetting it like that is to mask failure-to-set-it
mistakes.

src/backend/postmaster/postmaster.c

@@ -37,7 +37,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.591 2009/08/28 17:42:54 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.592 2009/08/28 18:23:53 tgl Exp $
  *
  * NOTES
  *
@@ -3353,7 +3353,6 @@ BackendRun(Port *port)
 	int			ac;
 	long		secs;
 	int			usecs;
-	char		protobuf[32];
 	int			i;
 
 	/*
@@ -3397,10 +3396,6 @@ BackendRun(Port *port)
 	 */
 	split_opts(av, &ac, ExtraOptions);
 
-	/* Tell the backend what protocol the frontend is using. */
-	snprintf(protobuf, sizeof(protobuf), "-v%u", port->proto);
-	av[ac++] = protobuf;
-
 	/*
 	 * Tell the backend it is being called from the postmaster, and which
 	 * database to use.  -y marks the end of secure switches.