go/zodb/btree: Minor cosmetics

- Refer to zodb interfaces as zodb.<name>;
- in tests bmapping is about LOBTree, not BTree. This fixes up c1ba9a90
  (go/zodb/btree: Turn it into template).

go/zodb/btree/btree.go.in

 // Copyright (c) 2001, 2002 Zope Foundation and Contributors.
 // All Rights Reserved.
 //
-// Copyright (C) 2018  Nexedi SA and Contributors.
+// Copyright (C) 2018-2019  Nexedi SA and Contributors.
 //                          Kirill Smelkov <kirr@nexedi.com>
 //
 // This software is subject to the provisions of the Zope Public License,
@@ -229,14 +229,14 @@ func (b *Bucket) get(key KEY) (interface{}, bool) {
 
 type bucketState Bucket // hide state methods from public API
 
-// DropState implements Stateful to discard bucket state.
+// DropState implements zodb.Stateful to discard bucket state.
 func (b *bucketState) DropState() {
 	b.next = nil
 	b.keys = nil
 	b.values = nil
 }
 
-// PySetState implements PyStateful to set bucket data from pystate.
+// PySetState implements zodb.PyStateful to set bucket data from pystate.
 func (b *bucketState) PySetState(pystate interface{}) (err error) {
 	t, ok := pystate.(pickle.Tuple)
 	if !ok {

go/zodb/btree/btree_test.go

-// Copyright (C) 2018  Nexedi SA and Contributors.
+// Copyright (C) 2018-2019  Nexedi SA and Contributors.
 //                          Kirill Smelkov <kirr@nexedi.com>
 //
 // This program is free software: you can Use, Study, Modify and Redistribute
@@ -50,7 +50,7 @@ type testEntry struct {
 	itemv []kv
 }
 
-// bmapping represents Get of Bucket or BTree.
+// bmapping represents LOBTree or a LOBucket wrapper.
 type bmapping interface {
 	Get(context.Context, int64) (interface{}, bool, error)
 }

go/zodb/btree/ziobtree.go

@@ -3,7 +3,7 @@
 // Copyright (c) 2001, 2002 Zope Foundation and Contributors.
 // All Rights Reserved.
 //
-// Copyright (C) 2018  Nexedi SA and Contributors.
+// Copyright (C) 2018-2019  Nexedi SA and Contributors.
 //                          Kirill Smelkov <kirr@nexedi.com>
 //
 // This software is subject to the provisions of the Zope Public License,
@@ -231,14 +231,14 @@ func (b *IOBucket) get(key int32) (interface{}, bool) {
 
 type iobucketState IOBucket // hide state methods from public API
 
-// DropState implements Stateful to discard bucket state.
+// DropState implements zodb.Stateful to discard bucket state.
 func (b *iobucketState) DropState() {
 	b.next = nil
 	b.keys = nil
 	b.values = nil
 }
 
-// PySetState implements PyStateful to set bucket data from pystate.
+// PySetState implements zodb.PyStateful to set bucket data from pystate.
 func (b *iobucketState) PySetState(pystate interface{}) (err error) {
 	t, ok := pystate.(pickle.Tuple)
 	if !ok {

go/zodb/btree/zlobtree.go

@@ -3,7 +3,7 @@
 // Copyright (c) 2001, 2002 Zope Foundation and Contributors.
 // All Rights Reserved.
 //
-// Copyright (C) 2018  Nexedi SA and Contributors.
+// Copyright (C) 2018-2019  Nexedi SA and Contributors.
 //                          Kirill Smelkov <kirr@nexedi.com>
 //
 // This software is subject to the provisions of the Zope Public License,
@@ -231,14 +231,14 @@ func (b *LOBucket) get(key int64) (interface{}, bool) {
 
 type lobucketState LOBucket // hide state methods from public API
 
-// DropState implements Stateful to discard bucket state.
+// DropState implements zodb.Stateful to discard bucket state.
 func (b *lobucketState) DropState() {
 	b.next = nil
 	b.keys = nil
 	b.values = nil
 }
 
-// PySetState implements PyStateful to set bucket data from pystate.
+// PySetState implements zodb.PyStateful to set bucket data from pystate.
 func (b *lobucketState) PySetState(pystate interface{}) (err error) {
 	t, ok := pystate.(pickle.Tuple)
 	if !ok {