Add a sign in as different user in SharePoint 2013

By default, the "Sign-in as different user" option is removed in the site. And this is a very useful function for development and testing purpose.

In the folder,
C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\15\TEMPLATE\CONTROLTEMPLATES

Edit the Welcome.ascx page to add the following link,
         <SharePoint:MenuItemTemplate runat="server" ID="ID_LoginAsDifferentUser"
                 Text="<%$Resources:wss,personalactions_loginasdifferentuser%>"
                 Description="<%$Resources:wss,personalactions_loginasdifferentuserdescription%>"
                 MenuGroupId="100"
                 Sequence="100"
                 UseShortId="true"
                 />
Done :)