Add access modifiers to `WP_Text_Diff_Renderer_Table` that are compatible with its parent class. Some of the inline docs suggest access that, if implemented, would produce fatal errors.

Add magic methods for BC: __get(), __set(), __isset(), __unset(), and __call().

See #27881, #22234.


git-svn-id: https://develop.svn.wordpress.org/trunk@28525 602fd350-edb4-49c9-b593-d223f7449a82