Mark deprecated methods as such in class reference

[Bernhard Reiter]

Currently, deprecated methods are only marked as such on their method reference page, e.g. ​https://developer.wordpress.org/reference/classes/wp_customize_image_control/add_tab/
It'd be great to see which methods in a class are deprecated on the class reference page (here: ​https://developer.wordpress.org/reference/classes/wp_customize_image_control/ )

[coffee2code]

In 1269:

developer.wordpress.org: Denote deprecated methods as such in a class's listing of its methods. Fixes #791