Deprecate calling `this._super` when there is no method on parent class.

We should not support calling _super when the parent class does not have a method defined (aka when there is no _super). This likely means adding a deprecation for now, and converting that to an error in 3.0.0.

Examples:

let A = Ember.Object.extend({
  foo() { return 'A - Foo'; },

  qux: Ember.computed(function() {
    return 'A - qux';
  })
});

let B = A.extend({
  bar() {
    // should trigger deprecation
    return this._super(...arguments) + '| B - Bar';
  },

  foo() {
    // should not trigger deprecation
    return this._super(...arguments) + ' | B - Foo | ' + this.bar();
  },

  qux: Ember.computed(function() {
    // should not trigger deprecation
    return this._super(...arguments) + ' | B - qux';
  }),

  baz: Ember.computed(function() {
    // should trigger deprecation
    return this._super(...arguments) + ' | B - baz';
  })
});

See original context

[locks]

I have to regularly audit the code for all addons to be sure I’m not breaking anything.

This is a thing you’re supposed to do.

[rwjblue]

This is still an issue, and we should issue an error…