X64: double stack size, to be able to have the same number of stack frames as in ia32.

Review URL: http://codereview.chromium.org/159852


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2617 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/execution.h

@@ -205,7 +205,7 @@ class StackGuard BASE_EMBEDDED {
   static void EnableInterrupts();
   static void DisableInterrupts();
 
-  static const uintptr_t kLimitSize = 512 * KB;
+  static const uintptr_t kLimitSize = kPointerSize * 128 * KB;
   static const uintptr_t kInterruptLimit = 0xfffffffe;
   static const uintptr_t kIllegalLimit = 0xffffffff;