Improve and reorder Fl_Tabs documentation

Note: this also removes the (not working) suggestion to add an invisible
box to an Fl_Scroll-type child of Fl_Tabs.

FL/Fl_Tabs.H

@@ -39,17 +39,6 @@ struct Fl_Menu_Item;
   other children are made invisible by calling hide() on them. Usually the
   children are Fl_Group widgets containing several widgets themselves.
 
-  \b Note: The widgets contained in each child should leave some clear space (five
-  pixels as of FLTK 1.4.0) at the top or bottom of the group where the tabs are
-  displayed, otherwise drawing the children may interfere with the separation
-  border between the tabs and the children. This is particularly important if the
-  child group is an Fl_Scroll widget: either the Fl_Scroll widget can be inset by
-  five pixels relative to other children or it must be ensured that the widgets
-  inside the Fl_Scroll group stay away from the top or bottom by this amount. You
-  can use an invisible Fl_Box at the top (or bottom) of the Fl_Scroll widget so
-  other (visible) widgets can't be scrolled all the way up or down to achieve this.
-  <!-- See GitHub issue #1175. -->
-
   Each child makes a card, and its label() is printed
   on the card tab, including the label font and style.  The
   selection color of that child is used to color the tab, while
@@ -65,6 +54,17 @@ struct Fl_Menu_Item;
   FLUID browser to select each child group and resize them until
   the tabs look the way you want them to.
 
+  \b Note: The widgets contained in each child should leave some clear space
+  (five pixels as of FLTK 1.4.x) at the top or bottom of the group (where the
+  tabs are displayed). Otherwise drawing the children may interfere with the
+  selection border between the tabs and the children. This is particularly
+  important if the child group is an Fl_Scroll widget: either the Fl_Scroll
+  widget must be inset by five pixels relative to other children or it can
+  be wrapped inside another Fl_Group and inset by five pixels within this
+  group so the contents of the Fl_Scroll widget are kept away from the tabs
+  by this amount.
+  <!-- See GitHub issue #1175. -->
+
   The background area behind and to the right of the tabs is
   "transparent", exposing the background detail of the parent. The
   value of Fl_Tabs::box() does not affect this area. So if Fl_Tabs is