Fix draggging paint in the overworld editor.

Turn off dragging windows except by their title bars.

(cherry picked from commit f11b86f)

util/imgui_impl_sdl.cpp

@@ -242,6 +242,7 @@ bool    ImGui_ImplSdlGL2_Init(SDL_Window* window)
     // Setup back-end capabilities flags
     ImGuiIO& io = ImGui::GetIO();
     io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;   // We can honor GetMouseCursor() values (optional)
+    io.ConfigWindowsMoveFromTitleBarOnly = true;
 
     // Keyboard mapping. ImGui will use those indices to peek into the io.KeyDown[] array.
     io.KeyMap[ImGuiKey_Tab] = SDL_SCANCODE_TAB;