State checking for extending abstract classes

还没有人认领这个 Issue。

Currently, reusing state refinements from an abstract superclass in a concrete class is not fully implemented, and gives an error like the one below.

Example for abstract class `java.net.URLConnection`:
```java
@ExternalRefinementsFor("java.net.URLConnection")
@StateSet({"setup", "connected"})
public interface URLConnectionRefinements {

@StateRefinement(to="setup(this)")
public void URLConnection(URL url);

@StateRefinement(from="setup(this)")
public void setDoInput(boolean doinput);

@StateRefinement(from="setup(this)", to="connected(this)")
public void connect();

@StateRefinement(from="connected(this)")
public Object getContent();

}
```

Extended in class `URLExt`:
```java
class URLExt extends URLConnection{

public URLExt(URL url){
super(url);
}

@Override
public void connect() throws IOException {
// TODO Auto-generated method stub
throw new UnsupportedOperationException("Unimplemented method 'connect'");
}

}```

Tested in:
```java
class Testurl {
void test() throws URISyntaxException, IOException {

URLExt u = new URLExt(new URI("http://example.com").toURL());
u.setDoInput(false); // should not be an error but it is
u.getContent(); // should be an error

}
}
```

使用 URLConnectionRefinements 注解、URLExt 和 Testurl 示例重现该报告。首先跟踪在 URLExt 上调用方法时，如何检查从 java.net.URLConnection 继承的状态细化。完成的标准是：setDoInput(false) 被接受，而 getContent() 被拒绝，因为对象尚未达到已连接状态。

由索引模型根据 Issue 内容生成。