message: Use const_iterator in DWARFUnit
  Function DWARFUnit::GetDIE is using m_die_array only for reading so it can use
  DWARFDebugInfoEntry::const_iterator.
diff: @@ -450,9 +450,9 @@ DWARFUnit::GetDIE(dw_offset_t die_offset) {
  if (ContainsDIEOffset(die_offset)) {
  ExtractDIEsIfNeeded(false);
  - DWARFDebugInfoEntry::iterator end = m_die_array.end();
  - DWARFDebugInfoEntry::iterator pos =
  - lower_bound(m_die_array.begin(), end, die_offset, CompareDIEOffset);
  + DWARFDebugInfoEntry::const_iterator end = m_die_array.cend();
  + DWARFDebugInfoEntry::const_iterator pos =
  + lower_bound(m_die_array.cbegin(), end, die_offset, CompareDIEOffset);
  if (pos != end) {
  if (die_offset == (*pos).GetOffset())
  return DWARFDIE(this, &(*pos));
  