libvpx: Pull from upstream

source/libvpx/third_party/libmkv/EbmlBufferWriter.c

 // #include <strmif.h>
 #include "EbmlBufferWriter.h"
 #include "EbmlWriter.h"
 // #include <cassert>
 // #include <limits>
 // #include <malloc.h>  //_alloca
 #include <stdlib.h>
 #include <wchar.h>
 #include <string.h>
 
 void Ebml_Write(EbmlGlobal *glob, const void *buffer_in, unsigned long len) {
   unsigned char *src = glob->buf;
   src += glob->offset;
   memcpy(src, buffer_in, len);
   glob->offset += len;
 }
 
 static void _Serialize(EbmlGlobal *glob, const unsigned char *p, const unsigned char *q) {
   while (q != p) {
     --q;
-
-    unsigned long cbWritten;
     memcpy(&(glob->buf[glob->offset]), q, 1);
     glob->offset++;
   }
 }
 
 void Ebml_Serialize(EbmlGlobal *glob, const void *buffer_in, unsigned long len) {
   // assert(buf);
 
   const unsigned char *const p = (const unsigned char *)(buffer_in);
   const unsigned char *const q = p + len;
@@ skipping 12 matching lines @@
 
 void Ebml_EndSubElement(EbmlGlobal *glob, EbmlLoc *ebmlLoc) {
   unsigned long long size = glob->offset - ebmlLoc->offset - 8;
   unsigned long long curOffset = glob->offset;
   glob->offset = ebmlLoc->offset;
   size |=  0x0100000000000000LLU;
   Ebml_Serialize(glob, &size, 8);
   glob->offset = curOffset;
 }