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;