[Isolates] Fix build on 64-bit version of Windows with vs2008

[Isolates] Fix build on 64-bit version of Windows with vs2008

Committed: http://code.google.com/p/v8/source/detail?r=7065

[Dmitry Titov, 2011-03-04 02:43:14]

The vs2008 barfed on same class declared with mixed struct/class keywords.

Also new threading stuff in shell.cc needs WIN32 define, which is not defined
for samples by default.

[Vitaly Repeshko, 2011-03-04 15:40:18]

LGTM