Add a test case for calling generic functions taking alias args with box types

Author: brson

src/test/run-pass/generic-alias-box.rs

@@ -0,0 +1,13 @@
+// xfail-boot
+// xfail-stage0
+
+fn id[T](&T t) -> T {
+  ret t;
+}
+
+fn main() {
+  auto expected = @100;
+  auto actual = id[@int](expected);
+  log *actual;
+  check (*expected == *actual);
+}