Fix for bug#4237.

Signed-off-by: Dhananjay <dhananjaynakrani@gmail.com>


Now with these changes, sensitive information like token and others will not be present in outgoing HTTP Requests. Also the [Bug Report](https://sourceforge.net/p/phpmyadmin/bugs/4237/) only mentioned URLs associated with SQL queries, but as I found out, token was present in almost all outgoing links (like Wiki, Documentation, etc..). That problem is also solved with these changes.

Whitelist check for domains in url.php has been added. I've tried to add as many valid domains into the [Whitelist](https://github.com/dhananjay92/phpmyadmin/blob/54813d8ddd34e3362ca64e3c56f67c2a4ca6064a/libraries/core.lib.php#L828) as I could. <b>Please point out if any domains have been missed.</b>

<i>Pardon me for previous unsuccessful Pulls. Being a total novice to development in open source world, I made some silly mistakes in previous Pulls...:sweat_smile: </i>

Hope this satisfies required standards..:smiley: