Add regression test

Author: oli-obk

tests/ui/feature-gates/version_check.rs

@@ -0,0 +1,9 @@
+//@ run-pass
+
+fn supports_feature(_: &str) -> Option<bool> {
+    Some(true)
+}
+
+fn main() {
+    assert_ne!(supports_feature("foobar"), None);
+}