Fix "error: cannot determine the type of this integer"

With the latest Rust master, there are a few errors:

```
src/parser.rs:409:22: 409:27 error: cannot determine the type of this integer; add a suffix to specify the type explicitly
src/parser.rs:409             for _ in range(0, 4) {
                                       ^~~~~
src/parser.rs:414:22: 414:27 error: cannot determine the type of this integer; add a suffix to specify the type explicitly
src/parser.rs:414             for _ in range(0, 5) {
                                       ^~~~~
src/parser.rs:432:18: 432:23 error: cannot determine the type of this integer; add a suffix to specify the type explicitly
src/parser.rs:432         for _ in range(0, 15) {
                                   ^~~~~
```