Previously, due to a change to fix bug 15608, Method#inspect output
changed for class methods:

Ruby 2.7
"#<Method: String.prepend(*)>"

Before change:
"#<Method: #<Class:Object>(Module)#prepend(*)>"

This is wrong because the Method object was created from String and
not Object. This is because the fix for bug 15608 assumed it was
being called on the singleton class of a instance, and would skip
the first singleton class until it got to the class itself.  For
class methods, this results in always using the superclass. Fix
behavior to not skip until the superclass if the singleton class
is the singleton class of a module or class.

After change:
"#<Method: #<Class:Object>(Module)#prepend(*)>"

Fixes [Bug #17428]

Has been deprecated since c73b6bd7ebd01133538c645566944132dbde4d13.
[Feature #17116] [ruby-dev:50945]

* Use the wrapper of rb_cObject instead of data access
* Replaced rest of extentions
* Updated the version guard for Data
* Added the version guard of rb_cData

Has been deprecated since 684bdf6171b76f5bc5e4f05926a5ab01ec2b4fd5.

Matz says in [ruby-core:83954] that Data should be an alias of Object.
Because rb_cData has not been deprecated, let us deprecate the constant
to make it a C-level synonym of rb_cObject.