Support new callable reference expressions in UAST

Manually mute the class literal test in apiCheck.kt; support for new class
literal expressions is postponed because it's not straightforward to combine
both unbound (Type::class) and bound (instance::class) class literals in one
UClassLiteralExpression: in Java they're two very different expressions
(Type.class and instance.getClass())

plugins/lint/lint-checks/src/com/android/tools/klint/checks/ApiDetector.kt

@@ -86,7 +86,7 @@ open class ApiDetector : Detector(), UastScanner {
         }
 
         override fun visitClassLiteralExpression(node: UClassLiteralExpression): Boolean {
-            val clazz = node.type.resolve(context)
+            val clazz = node.type?.resolve(context)
             if (clazz != null) {
                 checkVersion(context, node, clazz)
             }
@@ -430,4 +430,4 @@ open class ApiDetector : Detector(), UastScanner {
                         ApiDetector::class.java,
                         Scope.SOURCE_FILE_SCOPE))
     }
-}
+}