add HP aCC workaround

[SVN r10019]

include/boost/detail/select_type.hpp

@@ -19,7 +19,9 @@ namespace boost { namespace detail {
   // Template class if_true -- select among 2 types based on a bool constant expression
   // Usage:
   //   typename if_true<(bool_const_expression)>::template then<true_type, false_type>::type
-  template <bool> struct if_true
+
+  // HP aCC cannot deal with missing names for template value parameters
+  template <bool b> struct if_true
   {
       template <class T, class F>
       struct then { typedef T type; };