basic_parser is abstract, not CRTP (API Change):

* `basic_parser` now uses pure virtual member functions instead
  of the curiously recurring template pattern.

Actions Required:

* Change uses of the `basic_parser` type to omit the `Derived`
  template parameter

* Classes derived from `basic_parser` no longer need to friend
  the base.

* Virtual functions in the derived class may be marked `override`.

include/boost/beast/websocket/impl/error.hpp

@@ -41,8 +41,4 @@ make_error_condition(condition c);
 } // beast
 } // boost
 
-#ifdef BOOST_BEAST_HEADER_ONLY
-#include <boost/beast/websocket/impl/error.ipp>
-#endif
-
 #endif