Move WebM writing support out of vpxenc.c.

This is mainly a clean up patchset. It moves the WebM writing support
out of vpxenc and into its own source file. Changes to tools_common and
vpxdec result from relocation of shared bits of code.

Change-Id: Iee55d3285f56e0a548f791094fb14c5ac5346a26

webmenc.h

diff --git a/webmenc.h b/webmenc.h
new file mode 100644
index 0000000..d5efd9b
--- /dev/null
+++ b/webmenc.h
@@ -0,0 +1,87 @@
+/*
+ *  Copyright (c) 2013 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#ifndef WEBMENC_H_
+#define WEBMENC_H_
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#if defined(_MSC_VER)
+/* MSVS doesn't define off_t */
+typedef __int64 off_t;
+#else
+#include <stdint.h>
+#endif
+
+#include "tools_common.h"
+#include "vpx/vpx_encoder.h"
+
+typedef off_t EbmlLoc;
+
+struct cue_entry {
+  unsigned int time;
+  uint64_t loc;
+};
+
+struct EbmlGlobal {
+  int debug;
+
+  FILE *stream;
+  int64_t last_pts_ms;
+  vpx_rational_t framerate;
+
+  /* These pointers are to the start of an element */
+  off_t position_reference;
+  off_t seek_info_pos;
+  off_t segment_info_pos;
+  off_t track_pos;
+  off_t cue_pos;
+  off_t cluster_pos;
+
+  /* This pointer is to a specific element to be serialized */
+  off_t track_id_pos;
+
+  /* These pointers are to the size field of the element */
+  EbmlLoc startSegment;
+  EbmlLoc startCluster;
+
+  uint32_t cluster_timecode;
+  int cluster_open;
+
+  struct cue_entry *cue_list;
+  unsigned int cues;
+};
+
+/* Stereo 3D packed frame format */
+typedef enum stereo_format {
+  STEREO_FORMAT_MONO       = 0,
+  STEREO_FORMAT_LEFT_RIGHT = 1,
+  STEREO_FORMAT_BOTTOM_TOP = 2,
+  STEREO_FORMAT_TOP_BOTTOM = 3,
+  STEREO_FORMAT_RIGHT_LEFT = 11
+} stereo_format_t;
+
+void write_webm_seek_element(struct EbmlGlobal *ebml,
+                             unsigned int id,
+                             off_t pos);
+
+void write_webm_file_header(struct EbmlGlobal *glob,
+                            const vpx_codec_enc_cfg_t *cfg,
+                            const struct vpx_rational *fps,
+                            stereo_format_t stereo_fmt,
+                            unsigned int fourcc);
+
+void write_webm_block(struct EbmlGlobal *glob,
+                      const vpx_codec_enc_cfg_t *cfg,
+                      const vpx_codec_cx_pkt_t *pkt);
+
+void write_webm_file_footer(struct EbmlGlobal *glob, int hash);
+
+#endif  // WEBMENC_H_