SF bug #951482: New module: doc versus action

Strengthen the warnings about creating bogus objects using the new module.

Doc/lib/libnew.tex

@@ -11,6 +11,8 @@ creation functions. This is for use primarily in marshal-type functions,
 when a new object needs to be created ``magically'' and not by using the
 regular creation functions. This module provides a low-level interface
 to the interpreter, so care must be exercised when using this module.
+It is possible to supply non-sensical arguments which crash the
+interpreter when the object is used.
 
 The \module{new} module defines the following functions: