Add ULL postfix to FILE_SIZE_THRESHOLD to avoid using int

Otherwise, cli->size > FILE_SIZE_THRESHOLD uses 32-bit integer which
overflows with very large files. Use ULL to enforce 64-bits.

src/core.h

@@ -14,7 +14,7 @@ extern int max_clients;
 extern int num_clients;
 extern bool redirect;
 /* max_client logic only applies for files larger than 1024 bytes. */
-#define FILE_SIZE_THRESHOLD 1024
+#define FILE_SIZE_THRESHOLD 1024ULL
 
 enum tip_client_state {
 	TIP_CLIENT_PENDING		= 0,