Test for KT-2155 Run-time error accessing internal value from other package

#KT-2155 fixed

compiler/testData/codegen/multi/internalVisibility/a.kt

@@ -0,0 +1,3 @@
+package a
+
+val x: String = "OK"

compiler/testData/codegen/multi/internalVisibility/box.kt

@@ -0,0 +1 @@
+fun box() = a.x

compiler/tests/org/jetbrains/jet/codegen/MultiFileGenTest.java

@@ -31,4 +31,8 @@ public class MultiFileGenTest extends CodegenTestCase {
         blackBoxMultiFile("/multi/simple/box.kt", "/multi/simple/ok.kt");
         System.out.println(generateToText());
     }
+
+    public void testInternalVisibility() {
+        blackBoxMultiFile("/multi/internalVisibility/box.kt", "/multi/internalVisibility/a.kt");
+    }
 }