Add support for disabled menu items about cocos2d-iphone HOT 3 CLOSED

low priority.
enhancement.

patches are accepted

Attached is a patch that allows MenuItems to be disabled.

Disabled MenuItems will do nothing when selected, unselected, or activate are 
called.

MenuItemFont objects will render text as grey (RGB code 126,126,126) when 
disabled.

MenuItemImage has a new constructor that takes a disabledImage parameter. The 
old constructor is kept for 
backwards compatibility and simply passes on a nil object to disabledImage. If 
the MenuItemImage is 
disabled, disabledImage will be drawn unless its value is nil, in which case 
normalImage will be drawn.

Thanks to Ricardo for this amazing framework. We hope to release our game soon. 
:)

thanks,
patch included in r266
also included example in TestExample demo