Add printer test for lambda that might be confused for a self type

Author: allanrenucci

tests/pos/lambda.decompiled

@@ -3,6 +3,12 @@ out/posTestFromTasty/pos/lambda/foo/Foo.class
 --------------------------------------------------------------------------------
 package foo {
   class Foo() {
+    {
+      (x: Int) =>
+        {
+          2
+        }
+    }
     val a: Int => Int = (x: Int) => x.*(x)
   }
 }

tests/pos/lambda.scala

@@ -1,4 +1,7 @@
 package foo
 class Foo {
+  {
+    (x: Int) => 2
+  }
   val a = (x: Int) => x * x
 }