Fix building of snapshots on Windows.

The romoval of _HAS_EXCEPTIONS=0 from the source files was not fully complemented with changes to the compiler flags used for mksnapshot.
Review URL: http://codereview.chromium.org/67242

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1731 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

SConstruct

@@ -238,6 +238,7 @@ MKSNAPSHOT_EXTRA_FLAGS = {
   },
   'msvc': {
     'all': {
+      'CPPDEFINES': ['_HAS_EXCEPTIONS=0'],
       'LIBS': ['winmm', 'ws2_32']
     }
   }