Better handler_ptr (API Change):

fix #242

* Add public constructors
* Add handler_ptr::empty()
* Add handler_ptr::element_type
* Remove make_handler_ptr free function
* Compiler error if element_type is an array type
* handler_ptr::get() returns nullptr if no object is owned

include/beast/http/impl/parse.ipp

@@ -53,9 +53,8 @@ public:
 
     template<class DeducedHandler, class... Args>
     parse_op(DeducedHandler&& h, Stream& s, Args&&... args)
-        : d_(make_handler_ptr<data, Handler>(
-            std::forward<DeducedHandler>(h), s,
-                std::forward<Args>(args)...))
+        : d_(std::forward<DeducedHandler>(h),
+            s, std::forward<Args>(args)...)
     {
         (*this)(error_code{}, 0, false);
     }