file body reports short_read on eof

fixes #1818
fixes #1815
close #1821

test/beast/http/error.cpp

@@ -67,6 +67,7 @@ public:
         check("beast.http", error::bad_obs_fold);
 
         check("beast.http", error::stale_parser);
+        check("beast.http", error::short_read);
     }
 };