documentation improvements

doc/manual.txt

@@ -4384,6 +4384,8 @@ helper distinct or object type has to be used for one pointer type.
 operator `=`
 ------------
 
+**Note**: Overriding the assignment operator has not yet been implemented.
+
 This operator is the assignment operator. Note that in the contexts 
 like ``let v = expr``, ``var v = expr``, ``parameter = defaultValue`` or for
 parameter passing no assignment is performed. The ``override`` pragma is

doc/tut2.txt

@@ -438,18 +438,6 @@ module.  Example:
     echo "Got exception ", repr(e), " with message ", msg
 
 
-Exception hierarchy
--------------------
-
-If you want to create your own exceptions you can inherit from E_Base, but you
-can also inherit from one of the existing exceptions if they fit your purpose.
-The exception tree is:
-
-.. include:: exception_hierarchy_fragment.txt
-
-See the `system <system.html>`_ module for a description of each exception.
-
-
 Annotating procs with raised exceptions
 ---------------------------------------