Add testcases for item name conflict at the same path level.

src/test/compile-fail/item-name-overload.rs

@@ -0,0 +1,8 @@
+// -*- rust -*-
+
+mod foo {
+  fn bar[T](T f) -> int { ret 17; }
+  type bar[U, T] = tup(int, U, T);
+}
+
+fn main() {}