* TabControl.cs: Change SetTab so it adds the tabpage to the list

* TabControl.cs: Change SetTab so it adds the tabpage to the list
of controls if it isn't already there - was blowing up when doing
tabcontrol.TabPages[i]=new TabPage().
SetTab now does a replace by removing the page at the index.
Add a new InsertTab method that inserts a page in a given index
instead of replacing.
Implements TabPageCollection.Insert(int, TabPage).

2007-04-27  Andreia Gaita  <avidigal@novell.com>

svn path=/trunk/mcs/; revision=76404