make smtp/imap connect() return bool instead of c-int

src/dc_job.rs

@@ -317,7 +317,7 @@ unsafe fn dc_job_do_DC_JOB_SEND(context: &Context, job: &mut dc_job_t) {
         );
         let connected = context.smtp.lock().unwrap().connect(context, loginparam);
         dc_loginparam_unref(loginparam);
-        if 0 == connected {
+        if !connected {
             dc_job_try_again_later(job, 3i32, 0 as *const libc::c_char);
             current_block = 14216916617354591294;
         } else {