Add an XFAILed test for failing destructors

Issue #236

Author: brson

src/test/run-fail/unwind-resource-fail.rs

@@ -0,0 +1,12 @@
+// error-pattern:fail
+// xfail-test
+
+resource r(i: int) {
+    // What happens when destructors throw?
+    fail;
+}
+
+fn main() {
+    @0;
+    let r <- r(0);
+}