Clean up BeginCommand and related routines. BeginCommand and EndCommand

are now both invoked once per received SQL command (raw parsetree) from
pg_exec_query_string.  BeginCommand is actually just an empty routine
at the moment --- all its former operations have been pushed into tuple
receiver setup routines in printtup.c.  This makes for a clean distinction
between BeginCommand/EndCommand (once per command) and the tuple receiver
setup/teardown routines (once per ExecutorRun call), whereas the old code
was quite ad hoc.  Along the way, clean up the calling conventions for
ExecutorRun a little bit.

src/include/access/printtup.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: printtup.h,v 1.18 2001/11/05 17:46:31 momjian Exp $
+ * $Id: printtup.h,v 1.19 2002/02/27 19:35:40 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -18,9 +18,10 @@
 
 extern DestReceiver *printtup_create_DR(bool isBinary);
 
-extern void showatts(char *name, TupleDesc attinfo);
+extern void debugSetup(DestReceiver *self, int operation,
+					   const char *portalName, TupleDesc typeinfo);
 extern void debugtup(HeapTuple tuple, TupleDesc typeinfo,
-		 DestReceiver *self);
+					 DestReceiver *self);
 
 /* XXX this one is really in executor/spi.c */
 extern void spi_printtup(HeapTuple tuple, TupleDesc tupdesc,