Add a test for check_arg_count.

tests/compile-fail/check_arg_count.rs

@@ -0,0 +1,7 @@
+#![feature(core_intrinsics)]
+
+use std::intrinsics;
+
+fn main() {
+    unsafe { intrinsics::forget(); } //~ ERROR this function takes 1 argument but 0 arguments were supplied
+}