Add multiple content length error

fix #2468

test/beast/http/basic_parser.cpp

@@ -703,7 +703,7 @@ public:
         failgrind<P>(c(",\r\n"),                            error::bad_content_length);
         failgrind<P>(c("0,\r\n"),                           error::bad_content_length);
         failgrind<P>(m("Content-Length: 0\r\n"
-                        "Content-Length: 100\r\n"),         error::bad_content_length);
+                        "Content-Length: 100\r\n"),         error::multiple_content_length);
     }
 
     void

test/beast/http/error.cpp

@@ -65,6 +65,7 @@ public:
         check("beast.http", error::bad_chunk);
         check("beast.http", error::bad_chunk_extension);
         check("beast.http", error::bad_obs_fold);
+        check("beast.http", error::multiple_content_length);
 
         check("beast.http", error::stale_parser);
         check("beast.http", error::short_read);

test/beast/http/parser.cpp

@@ -378,7 +378,7 @@ public:
             response_parser<string_body> parser;
             error_code ec;
             parser.put(net::buffer(message), ec);
-            BEAST_EXPECTS(ec == error::bad_content_length, ec.message());
+            BEAST_EXPECTS(ec == error::multiple_content_length, ec.message());
         };
 
         // multiple contents lengths the same