Add basic infrastructure for protecting V8's heap when leaving the VM...

src/platform-nullos.cc

Index: src/platform-nullos.cc
===================================================================
--- src/platform-nullos.cc	(revision 1577)
+++ src/platform-nullos.cc	(working copy)
@@ -173,6 +173,20 @@
 }
 
 
+#ifdef ENABLE_HEAP_PROTECTION
+
+void OS::Protect(void* address, size_t size) {
+  UNIMPLEMENTED();
+}
+
+
+void OS::Unprotect(void* address, size_t size, bool is_executable) {
+  UNIMPLEMENTED();
+}
+
+#endif
+
+
 void OS::Sleep(int milliseconds) {
   UNIMPLEMENTED();
 }