Move version macros to public V8 header.

include/v8config.h

Index: include/v8config.h
diff --git a/include/v8config.h b/include/v8config.h
index 0993a9f3e4fd9b7e13e8ca8eda8f83bb987a5bcd..adc4e3cf7306b0c6f303b506a60d1c44cba37fa6 100644
--- a/include/v8config.h
+++ b/include/v8config.h
@@ -444,4 +444,13 @@ namespace v8 { template <typename T> class AlignOfHelper { char c; T t; }; }
 # define V8_ALIGNOF(type) (sizeof(::v8::AlignOfHelper<type>) - sizeof(type))
 #endif
 
+
+// This macro accepts another macro or a string and converts it into a string
+// after preprocessor argument expansion.
+// Use like:
+//  #define AGE 42
+//  const gchar* greeting = V8_STRINGIFY(AGE) " today!";
+#define V8_STRINGIFY(macro_or_string) V8_STRINGIFY_ARG(macro_or_string)
+#define V8_STRINGIFY_ARG(contents)    #contents
+
 #endif  // V8CONFIG_H_