Upstream fix to dictionary properties access to V8

[misterdjules]

The lastest update to mdb_v8 in v0.12 fixed dictionary properties access. This commit touches deps/v8/tools/gen-postmortem-metadata.py with the following changes:

    'Map, instance_size, int, kInstanceSizeOffset',
     'Map, bit_field, char, kBitFieldOffset',
     'Map, bit_field2, char, kBitField2Offset',
-    'Map, bit_field3, SMI, kBitField3Offset',
+    'Map, bit_field3, int, kBitField3Offset',
     'Map, prototype, Object, kPrototypeOffset',
     'NameDictionaryShape, prefix_size, int, kPrefixSize',
     'NameDictionaryShape, entry_size, int, kEntrySize',

These changes should probably be upstreamed to V8.

[misterdjules]

cc @davepacheco