See discussion at https://groups.google.com/forum/?fromgroups#!topic/silverstripe-dev/Dodomh9QZjk
Fixes an access issue where all public methods on FormField were allowed,
and not checked for $allowed_actions. Before this patch you could e.g.
call FormField->Value() on the first field by using action_Value.
Removes the following assertion because it only worked due to RequestHandlingTest_AllowedControllerExtension
*not* having $allowed_extensions declared: "Actions on magic methods are only accessible if explicitly allowed on the controller."
allowed_actions is now only allowed to reference public methods defined
on the same Controller as the allowed_actions static, and
the wildcard "*" has been deprecated
This allows arguments to be passed along in an $allowed_actions deceleration of
the form 'action' => '->method' in the same way that arguments can be passed to
extension constructors when adding them using $extensions or
Object::add_extension.
I.e. 'action' => '->checkerMethod(false, 7, 2, "yesterday") would call the
checkerMethod method with the boolean false the numbers 7 and 2 and the string
"yesterday" as its arguments.
