Add a test that tests typestate checking inside of fn exprs.

src/test/compile-fail/fn-expr-type-state.rs

@@ -0,0 +1,11 @@
+// error-pattern:Unsatisfied precondition
+// xfail-stage0
+
+fn main() {
+    // Typestate should work even in a lambda. we should reject this program.
+    auto f = fn () -> int {
+        let int i;
+        ret i;
+    };
+    log_err f();
+}