Style: Enable window border by default. (#707)

imgui.cpp

@@ -724,7 +724,7 @@ ImGuiStyle::ImGuiStyle()
     Alpha                   = 1.0f;             // Global alpha applies to everything in ImGui
     WindowPadding           = ImVec2(8,8);      // Padding within a window
     WindowRounding          = 7.0f;             // Radius of window corners rounding. Set to 0.0f to have rectangular windows
-    WindowBorderSize        = 0.0f;             // Thickness of border around windows. Generally set to 0.0f or 1.0f. Other values not well tested.
+    WindowBorderSize        = 1.0f;             // Thickness of border around windows. Generally set to 0.0f or 1.0f. Other values not well tested.
     WindowMinSize           = ImVec2(32,32);    // Minimum window size
     WindowTitleAlign        = ImVec2(0.0f,0.5f);// Alignment for title bar text
     ChildRounding           = 0.0f;             // Radius of child window corners rounding. Set to 0.0f to have rectangular child windows