Correctly detect "about:" URI and ignore "file:///"

Test:
var validURI = linkPropsPlus.validURI;
var tests = {
	"http:": false,
	"http://": false,
	"file:///": false,
	"http://example.com": true,
	"https://example.com": true,
	"ftp://example.com/foo/bar": true,
	"http:example.com": false,
	"view-source:http://example.com": true,
	"view-source:https://example.com": true,
	"view-source:http": false,
	"view-source:http:": false,
	"jar:file:///C:/foo": true,
	"about:": true,
	"about:config": true,
	"about://config": false,
	"about:cache?device=memory": true,
	"unknownprotocol:foo": false,
	"unknownprotocol://bar": false,
	"Just invalid data": false,
	"yet-another-invalid": false,
	"yetanotherinvalid": false,
};
var failed = [];
for(var uri in tests) if(tests.hasOwnProperty(uri))
	if(validURI.test(uri) != tests[uri])
		failed.push(uri);
alert(failed.length ? "Failed!\n" + failed.join("\n") : "OK");