Support flexible types in DataFlowValues

compiler/testData/diagnostics/tests/platformTypes/dereference.kt

@@ -0,0 +1,28 @@
+// FILE: p/J.java
+
+package p;
+
+public class J {
+    public J j() {return null;}
+
+    public <T> T foo() {return null;}
+    public <T extends J> T foo1() {return null;}
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test(j: J) {
+    j.j() : J
+    j.j().j()
+    j.j()!!.j()
+
+    val ann = j.foo<String>()
+    ann!!.length
+    ann.length
+
+    val a = j.foo<J>()
+    a!!.j()
+    a.j()
+}