Find Usages: Add tests for enum entries

idea/testData/findUsages/kotlin/findFunctionUsages/enumFunctionUsages.0.kt

@@ -0,0 +1,25 @@
+// PSI_ELEMENT: org.jetbrains.jet.lang.psi.JetNamedFunction
+// OPTIONS: usages
+enum class E {
+    {
+        foo(1)
+    }
+
+    open fun <caret>foo(n: Int): Int = n
+
+    O
+    A {
+        {
+            foo(1)
+        }
+
+        override fun foo(n: Int): Int = n + 1
+    }
+    B {
+        {
+            foo(1)
+        }
+
+        override fun foo(n: Int): Int = n + 2
+    }
+}

idea/testData/findUsages/kotlin/findFunctionUsages/enumFunctionUsages.results.txt

@@ -0,0 +1,3 @@
+Function call (13: 13) foo(1)
+Function call (20: 13) foo(1)
+Function call (5: 9) foo(1)