BSON: Reworked the binary_writer such that it precomputes the size of the BSON-output.

This way, the output_adapter can work on simple output iterators and no longer requires random access iterators.

test/src/unit-alt-string.cpp

@@ -102,16 +102,6 @@ class alt_string
         str_impl.resize(n, c);
     }
 
-    auto begin() -> std::string::iterator
-    {
-        return str_impl.begin();
-    }
-
-    auto end() -> std::string::iterator
-    {
-        return str_impl.end();
-    }
-
     template <typename op_type>
     bool operator<(const op_type& op) const
     {