message: Fix for border under title bar when WindowBorderSize == 0 and FrameBorderSize > 0
diff: @@ -4768,7 +4768,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
  window->DrawList->AddLine(border.Min, border.Max, GetColorU32(ImGuiCol_SeparatorActive), ImMax(1.0f, window_border_size));
  }
  if (style.FrameBorderSize > 0 && !(flags & ImGuiWindowFlags_NoTitleBar))
  - window->DrawList->AddLine(title_bar_rect.GetBL()+ImVec2(1,-1), title_bar_rect.GetBR()+ImVec2(-1,-1), GetColorU32(ImGuiCol_Border), style.FrameBorderSize);
  + window->DrawList->AddLine(title_bar_rect.GetBL() + ImVec2(style.WindowBorderSize, -1), title_bar_rect.GetBR() + ImVec2(-style.WindowBorderSize,-1), GetColorU32(ImGuiCol_Border), style.FrameBorderSize);
  }
  // Store a backup of SizeFull which we will use next frame to decide if we need scrollbars.
  