update opencontainers/image-spec to v1.0.0-rc3

Signed-off-by: Antonio Murdaca <runcom@redhat.com>

vendor/github.com/opencontainers/image-spec/specs-go/v1/layout.go

@@ -0,0 +1,28 @@
+// Copyright 2016 The Linux Foundation
+//
+// 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 v1
+
+import "regexp"
+
+// ImageLayout is the structure in the "oci-layout" file, found in the root
+// of an OCI Image-layout directory.
+type ImageLayout struct {
+	Version string `json:"imageLayoutVersion"`
+}
+
+var (
+	// RefsRegexp matches requirement of image-layout 'refs' charset.
+	RefsRegexp = regexp.MustCompile(`^[a-zA-Z0-9-._]+$`)
+)