notify about refs to foreign types (IDEA-145186)

java/java-tests/testData/inspection/unusedLibrary/usedJunitFromField/expected.xml

@@ -0,0 +1,3 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<problems/>
+

java/java-tests/testData/inspection/unusedLibrary/usedJunitFromField/src/MyTest.java

@@ -0,0 +1,4 @@
+import junit.framework.TestCase;
+public class MyTest {
+  TestCase myTestCase;
+}