Move version macros to public V8 header.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index c94e5105e0e5cffbc70d7a2012543dba77ee9e2f..fe715b0fecd611f1740e842ea61e030fd70383ba 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -79,6 +79,81 @@
 #endif  // V8_OS_WIN
 
 /**
+ * The major version number of the V8 library.
+ */
+#define V8_MAJOR_VERSION     3
+
+/**
+ * The minor version number of the V8 library.
+ */
+#define V8_MINOR_VERSION     21
+
+/**
+ * The build number of the V8 library.
+ */
+#define V8_BUILD_NUMBER      8
+
+/**
+ * The patch level of the V8 library.
+ */
+#define V8_PATCH_LEVEL       0
+
+/**
+ * This is non-zero if the V8 library is a candidate version or zero for
+ * release versions.
+ */
+#define V8_CANDIDATE_VERSION 1
+
+/**
+ * \def V8_VERSION_STRING
+ * The version string of the V8 library.
+ */
+#if V8_CANDIDATE_VERSION && V8_PATCH_LEVEL
+# define V8_VERSION_STRING                        \
+    V8_STRINGIFY(V8_MAJOR_VERSION) "."            \
+    V8_STRINGIFY(V8_MINOR_VERSION) "."            \
+    V8_STRINGIFY(V8_BUILD_NUMBER) "."             \
+    V8_STRINGIFY(V8_PATCH_LEVEL) " (candidate)"
+#elif V8_PATCH_LEVEL
+# define V8_VERSION_STRING                        \
+    V8_STRINGIFY(V8_MAJOR_VERSION) "."            \
+    V8_STRINGIFY(V8_MINOR_VERSION) "."            \
+    V8_STRINGIFY(V8_BUILD_NUMBER) "."             \
+    V8_STRINGIFY(V8_PATCH_LEVEL)
+#elif V8_CANDIDATE_VERSION
+# define V8_VERSION_STRING                        \
+    V8_STRINGIFY(V8_MAJOR_VERSION) "."            \
+    V8_STRINGIFY(V8_MINOR_VERSION) "."            \
+    V8_STRINGIFY(V8_BUILD_NUMBER) " (candidate)"
+#else
+# define V8_VERSION_STRING                        \
+    V8_STRINGIFY(V8_MAJOR_VERSION) "."            \
+    V8_STRINGIFY(V8_MINOR_VERSION) "."            \
+    V8_STRINGIFY(V8_BUILD_NUMBER)
+#endif
+
+/**
+ * Checks the version of the V8 library that is being compiled against.
+ *
+ * Sample usage:
+ * \code
+ *    #if V8_CHECK_VERSION(3, 21, 8, 0)
+ *      // Code that requires V8 3.21.8.0 or later.
+ *      ...
+ *    #endif
+ * \endcode
+ */
+#define V8_CHECK_VERSION(major, minor, build, patch)  \
+    ((V8_MAJOR_VERSION * 1000000 +                    \
+      V8_MINOR_VERSION * 10000 +                      \
+      V8_BUILD_NUMBER * 100 +                         \
+      V8_PATCH_LEVEL) >=                              \
+     ((major) * 1000000 +                             \
+      (minor) * 10000 +                               \
+      (build) * 100 +                                 \
+      (patch)))
+
+/**
  * The v8 JavaScript engine.
  */
 namespace v8 {