Add %property (logo?).

I've added a %property directive to Logos. It follows the same syntax as the @property directive.

It creates a fast way to emulate ivars in hooked classes. It adds getter and setter methods, which use Objective-C associated objects as the backend. It only supports Objective-C objects at the moment, but it may be possible to store C types.

Supports the following property attributes:

assign
retain
copy
nonatomic
getter

The 'setter' attribute will be implemented soon.

Consider merging my additions?