tdf#93318 reintroduce first/last button in Calc tab bar

Seems that first/last button are still useful when there are a lot
of tabs. Using ctrl+click is not discoverable enough for the users
so for now bring the buttons back.
Also turn on enabling/disabling buttons when they have some
effect (this was turned off for Calc for unknown reasons).

Change-Id: I6bbb04d44066ebc6b89fe3d941ecafdbb378284a
(cherry picked from commit b6fe593c)
Reviewed-on: https://gerrit.libreoffice.org/19380Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>
Tested-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>

sc/source/ui/view/tabcont.cxx

@@ -38,7 +38,7 @@
 // STATIC DATA -----------------------------------------------------------
 
 ScTabControl::ScTabControl( vcl::Window* pParent, ScViewData* pData )
-    : TabBar(pParent, WB_3DLOOK | WB_MINSCROLL | WB_RANGESELECT | WB_MULTISELECT | WB_DRAG)
+    : TabBar(pParent, WB_3DLOOK | WB_MINSCROLL | WB_SCROLL | WB_RANGESELECT | WB_MULTISELECT | WB_DRAG)
     , DropTargetHelper(this)
     , DragSourceHelper(this)
     , pViewData(pData)
@@ -79,7 +79,7 @@ ScTabControl::ScTabControl( vcl::Window* pParent, ScViewData* pData )
     EnableEditMode();
     UpdateInputContext();
 
-    SetScrollAlwaysEnabled(true);
+    SetScrollAlwaysEnabled(false);
 
     SetScrollAreaContextHdl( LINK( this, ScTabControl, ShowPageList ) );
 }