fix Issue 13779 - gdb can't find frame base when using ld.gold

- missing relocation addend .debug_info reference to .debug_loc
add comment on #else branch
refactoring

- add dwarf_apprel32 to encapsulate the difference between relocations
  with addend (.rela, 64-bit) and those without addend (.rel, 32-bit)
Merge pull request #4168 from MartinNowak/fix13779

 fix Issue 13779 - gdb can't find frame base when using ld.gold