Fix the ambiguous integer literal error

This commit fixes this:

```
src/crypto/symm.rs:95:25: 95:52 error: cannot determine a type for
this expression: cannot determine the type of this integer; add a
suffix to specify the type explicitly [E0101]
src/crypto/symm.rs:95                 let v = if padding { 1 } else { 0 } as c_int;
```

rustc version: rustc 0.12.0-pre (566b470e1 2014-08-27 02:31:20 +0000)