Fix warnings on Win64.

SConstruct

 # Copyright 2008 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 255 matching lines @@
       'WARNINGFLAGS': ['/WX', '/wd4355', '/wd4800']
     },
     'library:shared': {
       'CPPDEFINES': ['BUILDING_V8_SHARED'],
       'LIBS': ['winmm', 'ws2_32']
     },
     'arch:ia32': {
       'WARNINGFLAGS': ['/W3']
     },
     'arch:x64': {
-      'WARNINGFLAGS': ['/W2']
+      'WARNINGFLAGS': ['/W3']
     },
     'arch:arm': {
       'CPPDEFINES':   ['V8_TARGET_ARCH_ARM'],
       # /wd4996 is to silence the warning about sscanf
       # used by the arm simulator.
       'WARNINGFLAGS': ['/wd4996']
     },
     'disassembler:on': {
       'CPPDEFINES':   ['ENABLE_DISASSEMBLER']
     }
@@ skipping 695 matching lines @@
 # version of scons.  Also, there's a bug in some revisions that
 # doesn't allow this flag to be set, so we swallow any exceptions.
 # Lovely.
 try:
   SetOption('warn', 'no-deprecated')
 except:
   pass
 
 
 Build()