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_opengl2_example/imgui_impl_sdl_gl2.h
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.h
#	imgui.cpp

examples/imgui_impl_win32.cpp

@@ -200,6 +200,11 @@ void    ImGui_ImplWin32_NewFrame()
     ImGui::NewFrame();
 }
 
+// Allow compilation with old Windows SDK. MinGW doesn't have default _WIN32_WINNT/WINVER versions.
+#ifndef WM_MOUSEHWHEEL
+#define WM_MOUSEHWHEEL 0x020E
+#endif
+
 // Process Win32 mouse/keyboard inputs. 
 // You can read the io.WantCaptureMouse, io.WantCaptureKeyboard flags to tell if dear imgui wants to use your inputs.
 // - When io.WantCaptureMouse is true, do not dispatch mouse input data to your main application.