Add two tests, one xfailed, for inferring lambda kinds in return position

src/test/run-pass/newlambdas-ret-infer.rs

@@ -0,0 +1,9 @@
+// Test that the lambda kind is inferred correctly as a return
+// expression
+
+fn shared() -> fn@() { ret || (); }
+
+fn unique() -> fn~() { ret || (); }
+
+fn main() {
+}

src/test/run-pass/newlambdas-ret-infer2.rs

@@ -0,0 +1,10 @@
+// xfail-test fn~ is not inferred
+// Test that the lambda kind is inferred correctly as a return
+// expression
+
+fn shared() -> fn@() { || () }
+
+fn unique() -> fn~() { || () }
+
+fn main() {
+}