Add a test that native mods don't need to declare an ABI

Author: brson

src/test/run-pass/native-no-abi.rs

@@ -0,0 +1,9 @@
+// ABI is cdecl by default
+
+native mod rustrt {
+    fn unsupervise();
+}
+
+fn main() {
+    rustrt::unsupervise();
+}