Summer of GUI: WTL

This month we will continue our Summer of GUI by looking at Windows Template Library (https://en.wikipedia.org/wiki/Windows_Template_Library) (WTL). WTL is a lightweight C++ wrapper around the Win32 API for creating desktop applications. It is similar in flavor to the Active Template Library (https://en.wikipedia.org/wiki/Active_Template_Library) (ATL), a lightweight library for creating COM objects.