Add access modifier to methods/members in `WP_Ajax_Response`. Adds a magic `__get()` method for BC.

See #27881, #22234.


git-svn-id: https://develop.svn.wordpress.org/trunk@28508 602fd350-edb4-49c9-b593-d223f7449a82
Add missing access modifiers to methods/members in `WP_Customize_*`.

See #27881, #22234.


git-svn-id: https://develop.svn.wordpress.org/trunk@28509 602fd350-edb4-49c9-b593-d223f7449a82
Add access modifiers to methods/members in `WP_Embed`.

See #27881, #22234.


git-svn-id: https://develop.svn.wordpress.org/trunk@28510 602fd350-edb4-49c9-b593-d223f7449a82
Add access modifiers to methods/members in `WP_Error`. Add a magic `__get()` method for BC.

See #27881, #22234.


git-svn-id: https://develop.svn.wordpress.org/trunk@28511 602fd350-edb4-49c9-b593-d223f7449a82