Support bucket versioning (#9377)

- Implement a new xl.json 2.0.0 format to support,
  this moves the entire marshaling logic to POSIX
  layer, top layer always consumes a common FileInfo
  construct which simplifies the metadata reads.
- Implement list object versions
- Migrate to siphash from crchash for new deployments
  for object placements.

Fixes #2111

cmd/bucket-versioning.go

@@ -0,0 +1,57 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+import "github.com/minio/minio/pkg/bucket/versioning"
+
+// BucketVersioningSys - policy subsystem.
+type BucketVersioningSys struct{}
+
+// Enabled enabled versioning?
+func (sys *BucketVersioningSys) Enabled(bucket string) bool {
+	vc, err := globalBucketMetadataSys.GetVersioningConfig(bucket)
+	if err != nil {
+		return false
+	}
+	return vc.Enabled()
+}
+
+// Suspended suspended versioning?
+func (sys *BucketVersioningSys) Suspended(bucket string) bool {
+	vc, err := globalBucketMetadataSys.GetVersioningConfig(bucket)
+	if err != nil {
+		return false
+	}
+	return vc.Suspended()
+}
+
+// Get returns stored bucket policy
+func (sys *BucketVersioningSys) Get(bucket string) (*versioning.Versioning, error) {
+	if globalIsGateway {
+		objAPI := newObjectLayerFn()
+		if objAPI == nil {
+			return nil, errServerNotInitialized
+		}
+		return nil, NotImplemented{}
+	}
+	return globalBucketMetadataSys.GetVersioningConfig(bucket)
+}
+
+// NewBucketVersioningSys - creates new versioning system.
+func NewBucketVersioningSys() *BucketVersioningSys {
+	return &BucketVersioningSys{}
+}