Construct the value of the Authorization header for an HTTP request.
function getAuthorizationHeader(realm, parameters) {
        var header = 'OAuth realm="' + OAuth.percentEncode(realm) + '"';
        var list = OAuth.getParameterList(parameters);
        for (var p = 0; p < list.length; ++p) {
            var parameter = list[p];
            var name = parameter[0];
            if (name.indexOf("oauth_") == 0) {
                header += ',' + OAuth.percentEncode(name) + '="' + OAuth.percentEncode(parameter[1]) + '"';
            }
        }
        return header;
    }