url: fix port overflow checking

This patch adds (port > 0xffff) check after each digit in the loop and
prevents integer overflow.

PR-URL: https://github.com/nodejs/node/pull/15794
Refs: https://github.com/w3c/web-platform-tests/pull/7602


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>