Merge branch 'master' into docking

# Conflicts:
#	backends/imgui_impl_metal.mm
#	backends/imgui_impl_opengl3.cpp
#	backends/imgui_impl_osx.mm
#	backends/imgui_impl_win32.cpp
#	docs/CHANGELOG.txt

backends/imgui_impl_dx9.cpp

@@ -322,6 +322,7 @@ void ImGui_ImplDX9_Shutdown()
     if (bd->pd3dDevice) { bd->pd3dDevice->Release(); }
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
+    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
     IM_DELETE(bd);
 }