[svn r118] Fixed dynamic casts.

Fixed a few interface bugs.

test/interface6.d

@@ -0,0 +1,44 @@
+module interface6;
+
+interface I
+{
+    void Ifunc();
+}
+
+interface J
+{
+    void Jfunc();
+}
+
+class C : I,J
+{
+    int i;
+    int j;
+    void Ifunc()
+    {
+        i++;
+    }
+    void Jfunc()
+    {
+        j++;
+    }
+}
+
+void main()
+{
+    C c = new C;
+    c.Ifunc();
+    c.Jfunc();
+    I i = c;
+    i.Ifunc();
+    J j = c;
+    j.Jfunc();
+    C c2 = cast(C)i;
+    c2.Ifunc();
+    c2.Jfunc();
+    C c3 = cast(C)j;
+    c3.Ifunc();
+    c3.Jfunc();
+    assert(c.i == 4);
+    assert(c.j == 4);
+}