Add FINAL and OVERRIDE macros for C++11 final/override.

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index 26fd53114c62d582501e5d37c2c7791cb60cd99b..7848c50ce503492948b8e573726f441b4a435132 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -375,6 +375,29 @@ F FUNCTION_CAST(Address addr) {
 #endif
 
 
+// Annotate a virtual method indicating it must be overriding a virtual
+// method in the parent class.
+// Use like:
+//   virtual void bar() OVERRIDE;
+#if __cplusplus >= 201103L

[Sven Panne, 2013/08/19 12:44:48]

Looking at Chrome's base/compiler_specific.h, I think we can use it more often:
MSVC supports this for ages (VS2005 at least) and clang supports it. Checking
the C++ version should be used as a fallback.

+#define OVERRIDE override
+#else
+#define OVERRIDE
+#endif
+
+
+// Annotate a virtual method indicating that subclasses must not override it,
+// or annotate a class to indicate that it cannot be subclassed.
+// Use like:
+//   class B FINAL : public A {};
+//   virtual void bar() FINAL;
+#if __cplusplus >= 201103L

[Sven Panne, 2013/08/19 12:44:48]

Same here: For MSVC we can fall back to 'sealed', clang has it, otherwise check
C++ version.

+#define FINAL final
+#else
+#define FINAL
+#endif
+
+
 #if defined(__GNUC__) && __GNUC__ >= 4
 #define MUST_USE_RESULT __attribute__ ((warn_unused_result))
 #else