update KDE guide link; added to the list of the 'Changes which are compatible' the addition of a ctor

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58308 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/tech/tn0020.txt

@@ -37,7 +37,7 @@ also section (4).
 -------------------------------------------------
 
 If its still up, the KDE guide is a good reference:
-http://developer.kde.org/documentation/other/binarycompatibility.html
+http://techbase.kde.org/Policies/Binary_Compatibility_Issues_With_C++
 
 The changes that are NOT binary compatible:
 - Adding a virtual function
@@ -63,6 +63,7 @@ even a default one)
 
 - Adding a new class
 - Adding a new non-virtual method to an existing class
+- Adding a new constructor to an existing class
 - Overriding the implementation of an existing virtual function
 [this is considered to be backwards binary compatible until we find a
  counter example; currently it's known to work with Apple gcc at least]