qmake - creating plugin bundle - option "plugin_bundle" is undocumented

For Mac there are special CONFIG options available and documented:
http://doc.qt.nokia.com/4.7-snapshot/qmake-variable-reference.html#config

a) app_bundle Puts the executable into a bundle (this is the default).
b) lib_bundle Puts the library into a library bundle

But there is one missing, the option called c) plugin_bundle. This flag is required in order to create plugin bundle. It would be useful to have it documented.
TEMPLATE = lib
CONFIG += plugin
CONFIG += plugin_bundle