Make sure to initialize all fields in the special maps...

Make sure to initialize all fields in the special maps
created during bootstrapping. Without this change we 
risk having weird flags set on the map for the null
value (among others), which can lead to crashes.

Committed: http://code.google.com/p/v8/source/detail?r=3725

[iposva, 2010-01-27 19:55:10]

LGTM, although it might be safer to initialize the whole memory area of the map
to zeros before continuing.

-Ivan

[Rico, 2010-01-28 08:14:47]

http://codereview.chromium.org/552195/diff/1/2
File src/heap.cc (right):

http://codereview.chromium.org/552195/diff/1/2#newcode1191
src/heap.cc:1191: reinterpret_cast<Map*>(result)->set_bit_field2(0);
After adding the extensible property to bit_field2 maybe this needs to be (same
as in AllocateMap):
map->set_bit_field2(1 << Map::kIsExtensible);
(default value for extensible is true)