Merge branch 'master' into docking

# Conflicts:
#	backends/imgui_impl_glfw.cpp
#	backends/imgui_impl_sdl.cpp
#	examples/example_emscripten_opengl3/main.cpp
#	examples/example_glfw_opengl2/main.cpp
#	examples/example_glfw_opengl3/main.cpp
#	examples/example_glfw_vulkan/main.cpp
#	examples/example_glut_opengl2/main.cpp
#	examples/example_sdl_directx11/main.cpp
#	examples/example_sdl_opengl2/main.cpp
#	examples/example_sdl_opengl3/main.cpp
#	examples/example_sdl_vulkan/main.cpp
#	examples/example_win32_directx10/main.cpp
#	examples/example_win32_directx11/main.cpp
#	examples/example_win32_directx12/main.cpp
#	examples/example_win32_directx9/main.cpp
#	imgui_demo.cpp

imgui_demo.cpp

@@ -6068,6 +6068,9 @@ void ImGui::ShowAboutWindow(bool* p_open)
 #ifdef __clang_version__
         ImGui::Text("define: __clang_version__=%s", __clang_version__);
 #endif
+#ifdef __EMSCRIPTEN__
+        ImGui::Text("define: __EMSCRIPTEN__");
+#endif
 #ifdef IMGUI_HAS_VIEWPORT
         ImGui::Text("define: IMGUI_HAS_VIEWPORT");
 #endif