Merge branch 'master' into viewport

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx12.cpp
#	examples/imgui_impl_dx9.cpp
#	examples/opengl2_example/imgui_impl_glfw_gl2.cpp
#	examples/opengl3_example/imgui_impl_glfw_gl3.cpp
#	examples/sdl_opengl2_example/imgui_impl_sdl_gl2.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp
#	examples/vulkan_example/imgui_impl_glfw_vulkan.cpp
#	imgui.h

examples/imgui_impl_opengl3.cpp

@@ -50,8 +50,9 @@ bool    ImGui_ImplOpenGL3_Init(const char* glsl_version)
     strcpy(g_GlslVersion, glsl_version);
     strcat(g_GlslVersion, "\n");
 
+    // Setup back-end capabilities flags
     ImGuiIO& io = ImGui::GetIO();
-    io.ConfigFlags |= ImGuiConfigFlags_RendererHasViewports;
+    io.BackendFlags |= ImGuiBackendFlags_RendererHasViewports;    // We can create multi-viewports on the Renderer side (optional)
     if (io.ConfigFlags & ImGuiConfigFlags_EnableViewports)
         ImGui_ImplOpenGL3_InitPlatformInterface();
     return true;