Enable new version number format by default (see issue #2596)

To continue using the old format set the CEF_OLD_VERSION_FORMAT=1 environment
variable before building.

tools/cef_version.py

@@ -24,7 +24,7 @@ class VersionFormatter:
 
     # Whether to use the old version format by default.
     self._old_format_default = \
-        bool(int(os.environ.get('CEF_OLD_VERSION_FORMAT', '1')))
+        bool(int(os.environ.get('CEF_OLD_VERSION_FORMAT', '0')))
 
     self.reset()