Viewport, Platform: Added void* to render/swap buffer functions. Comments. (#1542, #1042)

examples/imgui_impl_opengl2.cpp

@@ -1,6 +1,9 @@
 // ImGui Renderer for: OpenGL2 (legacy OpenGL, fixed pipeline)
 // This needs to be used along with a Platform Binding (e.g. GLFW, SDL, Win32, custom..)
 
+// Implemented features:
+//  [X] User texture binding. Use 'GLUint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
+
 // **DO NOT USE THIS CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)**
 // **Prefer using the code in imgui_impl_opengl3.cpp**
 // This code is mostly provided as a reference to learn how ImGui integration works, because it is shorter to read.