Major V8 updates are usually API/ABI incompatible with previous
versions. This commit adapts NODE_MODULE_VERSION for V8 6.7.

Refs: https://github.com/nodejs/CTC/blob/master/meetings/2016-09-28.md

Refs: v8/v8@f9934aa
Fixes: nodejs#36

Synchronize source files list with upstream's BUILD.gn.

Adds `isBigInt64Array` and `isBigUint64Array`.

Also exclude isBigInt from test because `typeof value === 'bigint'` can
be used instead.

until
v8/v8@23d7fb6

Refs: nodejs#46

v8.getHeapSpaceStatistics() now includes read_only_space
in its results. Update test-v8-stats.js to account for this.

Fixes: nodejs#44

This commit updates the following postmortem metadata constants:

- v8dbg_class_SharedFunctionInfo__code__Code
  - This is now combined with SharedFunctionInfo's function_data.
  - Renamed: v8dbg_class_SharedFunctionInfo__function_data__Object
  - V8 commit: v8/v8@51ded9d

- v8dbg_class_SharedFunctionInfo__raw_name__Object and
- v8dbg_class_SharedFunctionInfo__scope_info__ScopeInfo
  - These are now combined as name_or_scope_info.
  - Renamed: v8dbg_class_SharedFunctionInfo__name_or_scope_info__Object
  - V8 commit: v8/v8@74a663b

Fixes: nodejs#44

until
v8/v8@b27ee43

This commit updates the following postmortem metadata constant:

- v8dbg_class_SharedFunctionInfo__compiler_hints__int
  - Renamed: v8dbg_class_SharedFunctionInfo__flags__int
  - V8 commit: v8/v8@071b01b#diff-f3f182b0510ba2ee39ae87e421ff110b

Fixes: nodejs#48

This commit renames V8DBG_CLASS_SHAREDFUNCTIONINFO__RAW_NAME__OBJECT
to V8DBG_CLASS_SHAREDFUNCTIONINFO__NAME_OR_SCOPE_INFO__OBJECT
following an upstream change.