Merge branch 'context'

# Conflicts:
#	examples/allegro5_example/main.cpp
#	examples/directx10_example/main.cpp
#	examples/directx11_example/main.cpp
#	examples/directx9_example/main.cpp
#	examples/marmalade_example/main.cpp
#	examples/opengl2_example/main.cpp
#	examples/opengl3_example/main.cpp
#	examples/sdl_opengl2_example/main.cpp
#	examples/sdl_opengl3_example/main.cpp
#	examples/vulkan_example/main.cpp

examples/marmalade_example/imgui_impl_marmalade.cpp

@@ -209,8 +209,6 @@ void    ImGui_Marmalade_InvalidateDeviceObjects()
 
 bool    ImGui_Marmalade_Init(bool install_callbacks)
 {
-    IwGxInit();
-
     ImGuiIO& io = ImGui::GetIO();
     io.KeyMap[ImGuiKey_Tab] = s3eKeyTab;                     // Keyboard mapping. ImGui will use those indices to peek into the io.KeyDown[] array.
     io.KeyMap[ImGuiKey_LeftArrow] = s3eKeyLeft;
@@ -251,8 +249,6 @@ bool    ImGui_Marmalade_Init(bool install_callbacks)
 void ImGui_Marmalade_Shutdown()
 {
     ImGui_Marmalade_InvalidateDeviceObjects();
-    ImGui::Shutdown();
-    IwGxTerminate();
 }
 
 void ImGui_Marmalade_NewFrame()