bug fix for OnUrlChange()

I had a problem with one of users using the Edit Link button and ending up with links like:
http://http//www.something.com

I discovered that half the time that I clicked browse and used Grant French's custom file manager it correctly set the url. The other half it left the http://.

I discovered that RegExp.exec doesn't reliably reset it's lastIndex property; so the RegExp.exec was starting from the point where it found the last match and missing the http://.

So in fck_link.js file's OnUrlChange() event add this line:
oRegex.UrlOnChangeProtocol.lastIndex = 0;

function OnUrlChange()
{
var sUrl = GetE('txtUrl').value ;
oRegex.UrlOnChangeProtocol.lastIndex = 0;
var sProtocol = oRegex.UrlOnChangeProtocol.exec( sUrl ) ;
if ( sProtocol )