Add dieoffset to missing location error messages.

Add dieoffset to missing location error messages.

* dwflpp.h (translate_location): Take die as argument.
  (find_struct_member): Take dies vector as argument.
* dwflpp.cxx (translate_location): Take die as argument and output dieoffset
  in error message.
  (find_struct_member): Take dies vector as argument and fill it with the
  dies found.
  (literal_stmt_for_local): Call translate_location with vardie.