message: imgcodecs: fix RBaseStream::setPos() outside of current block
  Seeking outside of the current block doesn't update actual data,
  so getByte()/etc will get wrong data from stalled buffer.
diff: @@ -175,8 +175,11 @@ void RBaseStream::setPos( int pos )
  }
  int offset = pos % m_block_size;
  + int old_block_pos = m_block_pos;
  m_block_pos = pos - offset;
  m_current = m_start + offset;
  + if (old_block_pos != m_block_pos)
  + readBlock();
  }
  