Java/C++/C#: Add field flow support for stores in nested fields.

java/ql/test/library-tests/dataflow/fields/D.java

@@ -0,0 +1,64 @@
+public class D {
+  Box2 boxfield;
+
+  public void f1() {
+    Elem e = new Elem();
+    Box2 b = new Box2(new Box1(null));
+    b.box.elem = e;
+    sinkWrap(b);
+  }
+
+  public void f2() {
+    Elem e = new Elem();
+    Box2 b = new Box2(new Box1(null));
+    b.box.setElem(e);
+    sinkWrap(b);
+  }
+
+  public void f3() {
+    Elem e = new Elem();
+    Box2 b = new Box2(new Box1(null));
+    b.getBox1().elem = e;
+    sinkWrap(b);
+  }
+
+  public void f4() {
+    Elem e = new Elem();
+    Box2 b = new Box2(new Box1(null));
+    b.getBox1().setElem(e);
+    sinkWrap(b);
+  }
+
+  public static void sinkWrap(Box2 b2) {
+    sink(b2.getBox1().getElem());
+  }
+
+  public void f5a() {
+    Elem e = new Elem();
+    boxfield = new Box2(new Box1(null));
+    boxfield.box.elem = e;
+    f5b();
+  }
+
+  private void f5b() {
+    sink(boxfield.box.elem);
+  }
+
+  public static void sink(Object o) { }
+
+  public static class Elem { }
+
+  public static class Box1 {
+    public Elem elem;
+    public Box1(Elem e) { elem = e; }
+    public Elem getElem() { return elem; }
+    public void setElem(Elem e) { elem = e; }
+  }
+
+  public static class Box2 {
+    public Box1 box;
+    public Box2(Box1 b) { box = b; }
+    public Box1 getBox1() { return box; }
+    public void setBox1(Box1 b) { box = b; }
+  }
+}