According to the System Center Configuration Manager Blog, the team has announced that they have released an update to the System Center 2012 R2 Configuration Manager SDK. The updated version of the SDK can download Clicking the Below Link
The mentioned update contains improvements and bug fixes to the Configuration Manager Client Messaging SDK (Microsoft.ConfigurationManagement.Messaging.dll). However, according to the ConfigMgr Team Highlighted that as part of this release, the Application Approval Workflow (AAW) solution accelerator has been removed from the SDK installer.
For further Information Kindly visit the System Center Configuration Manager Blog