Remove unused or obsolete classes and files

beast/http/headers.h

@@ -20,7 +20,7 @@
 #ifndef BEAST_HTTP_HEADERS_H_INCLUDED
 #define BEAST_HTTP_HEADERS_H_INCLUDED
 
-#include <beast/utility/ci_char_traits.h>
+#include <beast/ci_char_traits.h>
 #include <boost/intrusive/list.hpp>
 #include <boost/intrusive/set.hpp>
 #include <boost/iterator/transform_iterator.hpp>

beast/http/message.h

@@ -23,7 +23,7 @@
 #include <beast/http/basic_parser.h>
 #include <beast/http/method.h>
 #include <beast/http/headers.h>
-#include <beast/utility/ci_char_traits.h>
+#include <beast/ci_char_traits.h>
 #include <boost/intrusive/list.hpp>
 #include <boost/intrusive/set.hpp>
 #include <algorithm>

beast/http/method.h

@@ -20,6 +20,7 @@
 #ifndef BEAST_HTTP_METHOD_H_INCLUDED
 #define BEAST_HTTP_METHOD_H_INCLUDED
 
+#include <cassert>
 #include <memory>
 #include <string>