Clarify that variable-length argument lists of varadic template functions are ok.

rules.org

@@ -2278,10 +2278,8 @@ std::ostringstream  ost;
 
  - *Do not use the ellipsis notation for function arguments.*  [<<no-ellipsis>>]
 
-    Functions with an unspecified number of arguments should not be used
-    because they are a common cause of bugs that are hard to find. But
-    =catch(...)= to catch any exception is acceptable (but should generally
-    not be used outside of framework code).
+    Prior to C++ 11, functions with an unspecified number of arguments
+    had to be declared and used in a type-unsafe manner:
 
     #+BEGIN_EXAMPLE
 // avoid to define functions like:
@@ -2290,6 +2288,24 @@ void error(int severity, ...) // "severity" followed by a
                               // of char*s
 #+END_EXAMPLE
 
+    This method should be avoided.
+
+    As of C++ 11, one can accomplish something similar using varadic 
+    templates:
+
+    #+BEGIN_EXAMPLE
+template<typename ...ARGS>
+void error(int severity, ARGS...)
+#+END_EXAMPLE
+
+    This is fine, but should be used judiciously.  It's appropriate
+    for forwarding arguments theough a template function.  For other cases,
+    it's worth thinking if there might be a simpler way of doing things.
+
+    An ellipsis can also occur in a catch clause to catch any 
+    exception: =catch(...)=.  This is acceptable, but should generally
+    be restricted to framework-like code.
+
 
  - *Do not use preprocessor macros to take the place of functions, or for defining constants.* [<<no-macro-functions>>]
 
@@ -3022,6 +3038,8 @@ The comment includes the fact that it is the perpendicular distance.
 
 ** Version 0.8
  - Clarify that non-ascii characters should not be used in identifier names.
+ - Clarify that variable-length argument lists of varadic template functions
+   are ok.
 
 ** Version 0.7
  - Minor cleanups and updates to take into acount that we now require C++17.