Add long-while.rs to check on frame growth.

Author: graydon

src/test/run-pass/long-while.rs

@@ -0,0 +1,8 @@
+fn main() {
+  let int i = 0;
+  while (i < 1000000) {
+    i += 1;
+    auto x = 3;
+  }
+}
+