Update ODK library for OPK compatibility

This is a merge from http://go/wvgerrit of several changes to the ODK
library that allow it to be used in the same compilation unit as the
OPK serialization/deserialization code.

Merge of:
http://go/wvgerrit/104403
http://go/wvgerrit/105663
http://go/wvgerrit/106004
http://go/wvgerrit/107903
http://go/wvgerrit/107985
http://go/wvgerrit/110167
http://go/wvgerrit/110403
http://go/wvgerrit/110423
http://go/wvgerrit/110663
http://go/wvgerrit/110703
http://go/wvgerrit/110985
http://go/wvgerrit/111703
http://go/wvgerrit/112563
http://go/wvgerrit/113243
http://go/wvgerrit/115204
http://go/wvgerrit/117803
http://go/wvgerrit/121949

bug: 174518179
bug: 175920940
bug: 175126254
Change-Id: I433459182043ca43a040cdbc16d04f2b8215067a

libwvdrmengine/oemcrypto/odk/src/odk_message_priv.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2019 Google LLC. All Rights Reserved. This file and proprietary
+ * source code may only be used and distributed under the Widevine Master
+ * License Agreement.
+ */
+
+#ifndef WIDEVINE_ODK_INCLUDE_ODK_MESSAGE_PRIV_H_
+#define WIDEVINE_ODK_INCLUDE_ODK_MESSAGE_PRIV_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * This file must only be included by odk_message.c and serialization_base.c.
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+
+/*
+ * This is the implementation of a message. This structure is private, i.e. it
+ * should only be included by files that are allowed to modify the internals of
+ * a message, that being odk_message.c and serialization_base.c. To ensure
+ * proper alignment and message size, an ODK_Message_Impl should never be
+ * allocated directly, instead allocate ODK_Message and cast to ODK_Message_Impl
+ * because ODK_Message_Impl may be smaller than ODK_Message.
+ */
+typedef struct {
+  uint8_t* base;
+  size_t capacity;
+  size_t size;
+  size_t read_offset;
+  ODK_MessageStatus status;
+} ODK_Message_Impl;
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#endif  // WIDEVINE_ODK_INCLUDE_ODK_MESSAGE_PRIV_H_