Merge branch 'master' into docking

# Conflicts:
#	backends/imgui_impl_glfw.cpp
#	backends/imgui_impl_sdl.cpp
#	backends/imgui_impl_vulkan.cpp
#	backends/imgui_impl_vulkan.h
#	backends/imgui_impl_win32.cpp
#	imgui.cpp
#	imgui.h
#	imgui_demo.cpp
#	imgui_internal.h