examples/rust: Amend upload-reflector for recent changes

The previous commit changed uwr_get_http_content_len() to return a u64
to allow for uploads larger than 4GiB, which now means this generates
compiler errors about type mismatches, expected usize got u64.

Cast the return value of uwr_get_http_content_len() to usize to match
that of TOTAL_RESPONSE_SENT.

(Making TOTAL_RESPONSE_SENT a u64 creates a larger trail of problems).

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

Author: ac000

examples/rust/upload-reflector/src/lib.rs

@@ -65,7 +65,8 @@ pub fn upload_reflector(ctx: *mut luw_ctx_t) -> i32 {
 
     uwr_http_send_response(ctx);
 
-    if unsafe { TOTAL_RESPONSE_SENT == uwr_get_http_content_len(ctx) } {
+    if unsafe { TOTAL_RESPONSE_SENT == uwr_get_http_content_len(ctx) as usize }
+    {
         // Tell Unit no more data to send
         uwr_http_response_end();
     }