RT#22696: fix (probably harmless) warning

Regression from 36e28bf.  The cursors
generated internally by the collection loaders don't go through the
front door, so we don't know that they are selecting extra columns and
hence have to go through ->read_object().

lib/Tangram/Cursor.pm

@@ -288,11 +288,18 @@ sub _next
 
 	    my $obj = $storage->{objects}{$id};
 
-	    # even if object is already loaded we must read it so
-	    # that @row only contains residue, with -retrieve
-	    if ( !defined($obj) or $self->{-retrieve} ) {
+	    # even if object is already loaded we must read it so that
+	    # @row only contains residue, with -retrieve, and so that
+	    # any foreign/intrusive collections can get the
+	    # information they need.
+	    if ( !defined($obj) or $self->{-retrieve} or
+		 $self->{-no_skip_read} ) {
+		print $Tangram::TRACE __PACKAGE__.": reading object $id\n"
+		    if $Tangram::TRACE and $Tangram::DEBUG_LEVEL > 0;
 		$obj = $storage->read_object($id, $class, $state);
 	    } else {
+		print $Tangram::TRACE __PACKAGE__.": not reading object $id\n"
+		    if $Tangram::TRACE and $Tangram::DEBUG_LEVEL > 0;
 		# just pretend we did it.
 		@row = ();
 	    }

lib/Tangram/Type/Array/FromMany.pm

@@ -117,6 +117,7 @@ sub cursor
 	$cursor->{-coll_cols} = "t$coll_tid.$slot_col";
 	$cursor->{-coll_from} = "$table t$coll_tid";
 	$cursor->{-coll_where} = "t$coll_tid.$coll_col = $coll_id AND t$coll_tid.$item_col = t$item_tid.$storage->{schema}{sql}{id_col}";
+	$cursor->{-no_skip_read} = 1;
 
 	return $cursor;
 }

lib/Tangram/Type/Hash/FromMany.pm

@@ -139,6 +139,7 @@ sub cursor						# ?? factorize ??
     $cursor->{-coll_cols} = "t$coll_tid.$slot_col";
     $cursor->{-coll_from} = "$table t$coll_tid";
     $cursor->{-coll_where} = "t$coll_tid.$coll_col = $coll_id AND t$coll_tid.$item_col = t$item_tid.$storage->{schema}{sql}{id_col}";
+    $cursor->{-no_skip_read} = 1;
 
     return $cursor;
 }

lib/Tangram/Type/Set/FromMany.pm

@@ -132,6 +132,7 @@ sub demand
 		$cursor->{-coll_tid} = $coll_tid;
 		$cursor->{-coll_from} = "$table t$coll_tid";
 		$cursor->{-coll_where} = "t$coll_tid.$coll_col = $coll_id AND t$coll_tid.$item_col = t$item_tid.$storage->{schema}{sql}{id_col}";
+	    $cursor->{-no_skip_read} = 1;
 
 		$set->insert($cursor->select);
 	}