Add new minimal test for current blocker on bootstrapping.

Author: graydon

src/test/run-pass/tag-and-generic-obj.rs

@@ -0,0 +1,12 @@
+// xfail-stage0
+
+tag colour { red; green; }
+
+obj foo[T]() {
+  fn meth(&T x) {
+  }
+}
+
+fn main() {
+  foo[colour]().meth(red);
+}