Make wxToolBar styles consistent and add wxTB_DEFAULT_STYLE.

Don't include wxBORDER_NONE in neither wxToolBar ctor and Create() nor
wxFrame::CreateToolBar() flags parameter, override GetDefaultBorder() in
wxToolBar itself instead to use the border style appropriate for the current
platform by default. This has the same effect -- the default border style is
used unless another one is explicitly specified -- but is more clear and
consistent.

Also add wxTB_DEFAULT_STYLE for consistency with the other classes.

Closes #15037.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73757 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/framecmn.cpp

@@ -562,7 +562,7 @@ wxToolBar* wxFrameBase::CreateToolBar(long style,
         //      a) this allows us to have different defaults for different
         //         platforms (even if we don't have them right now)
         //      b) we don't need to include wx/toolbar.h in the header then
-        style = wxBORDER_NONE | wxTB_HORIZONTAL | wxTB_FLAT;
+        style = wxTB_DEFAULT_STYLE;
     }
 
     SetToolBar(OnCreateToolBar(style, id, name));