Handling of parsing errors

[JeromeMartinez]

Earlier discussion with @dericed

If there is a parsing problem (e.g. invalid EBML code), current behavior os

<block offset="81534" name="SimpleBlock" size="11049">
  <block offset="81534" name="Header" size="3">
    <data offset="81534" name="Name">35</data>
    <data offset="81535" name="Size">11046</data>
  </block>
  <block offset="81537" name="Problem" size="11046">
    <block offset="89775" name="Header" size="11046">
      <data offset="81537" name="Name">2</data>
      <data offset="103628" name="EBML integer parsing error">0</data>
    </block>
  </block>
</block>

Such issue should maybe not be in a block, but marked as error (e.g. <message type=“parsing error”>)