Update selector-css2.js

Corrected a buggy implementation of getElementsByTagName (useful on agents who don't support getEBTN on document fragments).
    
    var doc, find;

    // YUI's old implementation
    find = function(root, tagName) {
        var nodes = [], child = root.firstChild;    
        while (child) {
            // only collect HTMLElements
            // match tag to supplement missing getElementsByTagName
            if (child.tagName && (tagName === '*' || child.tagName === tagName)) {
                nodes.push(child);
            }
            child = child.nextSibling || child.firstChild;
        }
        return nodes;
    };

    doc = window.document;

    console.log(doc.getElementsByTagName("*").length);
    console.log(find(doc, "*").length);

As you can see, a large number of nodes are missed in the buggy version.