Add version macros.

tools/release/merge_to_branch.py

Index: tools/release/merge_to_branch.py
diff --git a/tools/release/merge_to_branch.py b/tools/release/merge_to_branch.py
index 7aa9fb6ab68c124f63eddda067d0f91149c4c5b5..5fe3ba42516ea9b6004ee925e3a0bae8e3ebd005 100755
--- a/tools/release/merge_to_branch.py
+++ b/tools/release/merge_to_branch.py
@@ -169,12 +169,12 @@ class IncrementVersion(Step):
     if self._options.revert_master:
       return
     new_patch = str(int(self["patch"]) + 1)
-    if self.Confirm("Automatically increment PATCH_LEVEL? (Saying 'n' will "
+    if self.Confirm("Automatically increment V8_PATCH_LEVEL? (Saying 'n' will "
                     "fire up your EDITOR on %s so you can make arbitrary "
                     "changes. When you're done, save the file and exit your "
                     "EDITOR.)" % VERSION_FILE):
       text = FileToText(os.path.join(self.default_cwd, VERSION_FILE))
-      text = MSub(r"(?<=#define PATCH_LEVEL)(?P<space>\s+)\d*$",
+      text = MSub(r"(?<=#define V8_PATCH_LEVEL)(?P<space>\s+)\d*$",
                   r"\g<space>%s" % new_patch,
                   text)
       TextToFile(text, os.path.join(self.default_cwd, VERSION_FILE))