Missing constants for postmortem metadata

[targos]

CI run: https://ci.nodejs.org/job/node-test-commit-node-v8/252/

Missing constants:

• v8dbg_bit_field3_dictionary_map_shift
• v8dbg_class_Map__inobject_properties_or_constructor_function_index__int
• v8dbg_class_Map__instance_attributes__int
• v8dbg_class_Map__instance_size__int

/cc @nodejs/post-mortem

[cjihrig]

PR coming up

[cjihrig]

Fix in #34