Change second occurrence of the same code in mp_count.hpp to match

Author: pdimov

include/boost/mp11/detail/mp_count.hpp

@@ -98,9 +98,9 @@ template<template<class...> class P, class... T> constexpr std::size_t cx_count_
 
     std::size_t r = 0;
 
-    for( std::size_t i = 1; i < sizeof...(T) + 1; ++i )
+    for( std::size_t i = 0; i < sizeof...(T); ++i )
     {
-        r += a[ i ];
+        r += a[ i+1 ];
     }
 
     return r;