Fixing all Undefine_Type== tests

This does not solve the whole issue. Previous version of slang
allowed that Undefined_Types can be passed arround as long as they
are not actively used. Somthing like this was okay:

variable undefined_var;

define test (a,b)
{
  return a*100;
}

test(5, undefined_var);

The current devel version of slang throws an error as soon as the
undefined type interacts with the stack. So the above code is not
valid any more.