Merge branch 'master' into viewport

# Conflicts:
#	examples/example_glfw_opengl3/main.cpp
#	examples/imgui_impl_opengl3.cpp
#	imgui.cpp
#	imgui_internal.h

examples/imgui_impl_vulkan.h

@@ -16,6 +16,7 @@
 
 #define IMGUI_VK_QUEUED_FRAMES      2
 
+// Please zero-clear before use.
 struct ImGui_ImplVulkan_InitInfo
 {
     VkInstance                      Instance;