When generating documentation for a class which extends a built-in PHP class or implements a built-in PHP library, it would be nice to inherit the built-in documentation.
We currently do this for classes that are not built-in. For example, in the following example class `B` will inherit the documentation for the `someMethod` method from class `A`.
```lang=php
abstract class A {
/*
* Documentation goes here.
*/
public function someMethod() {}
}
final class B extends A {
public function someMethod() {}
}
```
Consider @{class:PhutilArray} as another example. It would be nice if this class inherited documentation for the `offsetExists` method from http://php.net/manual/en/arrayaccess.offsetexists.php.