Fix compile on clamav 1.0

[kpcyrd]

Fixes this error:

error[E0308]: mismatched types
   --> /home/user/.cargo/registry/src/github.com-1ecc6299db9ec823/clamav-rs-0.5.5/src/error.rs:23:47
    |
23  |             let ptr = clamav_sys::cl_strerror(self.code);
    |                       ----------------------- ^^^^^^^^^ expected enum `cl_error_t`, found `i32`
    |                       |
    |                       arguments to this function are incorrect
    |
note: function defined here
   --> /home/user/repos/kpcyrd/libredefender/target/debug/build/clamav-sys-32481c721146e509/out/bindings.rs:305:12
    |
305 |     pub fn cl_strerror(clerror: cl_error_t) -> *const ::std::os::raw::c_char;
    |            ^^^^^^^^^^^

For more information about this error, try `rustc --explain E0308`.