Create a closure for deprecated code.

// This means Ext.oldMethod is only supported in 4.0.0beta and older.
// If Ext.getVersion('extjs') returns a version that is later than '4.0.0beta', for example '4.0.0RC',
// the closure will not be invoked
Ext.deprecate('extjs', '4.0.0beta', function() {
Ext.oldMethod = Ext.newMethod;

...
});

@param {String} packageName The package name
@param {String} since The last version before it's deprecated
@param {Function} closure The callback function to be executed with the specified version is less than the current version
@param {Object} scope The execution scope (`this`) if the closure
function(packageName, since, closure, scope) {
            if (Version.compare(Ext.getVersion(packageName), since) < 1) {
                closure.call(scope);
            }
        }