fgetln: Include <stdio.h> after <sys/*>

The <sys/*> headers tend to define things that might be used by other
headers, so while they should be self-contained, it is better to simply
include them first.

src/fgetln.c

@@ -25,10 +25,11 @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include <stdio.h>
 #include <sys/cdefs.h>
 #include <sys/types.h>
+
 #include <string.h>
+#include <stdio.h>
 
 #include "local-link.h"