Fix unused variable warnings

include/beast/http/impl/fields.ipp

@@ -230,7 +230,7 @@ template<class Allocator>
 template<class String>
 void
 basic_fields<Allocator>::reader::
-prepare(String& s, basic_fields const& f,
+prepare(String& s, basic_fields const&,
     unsigned version, verb v)
 {
     if(v == verb::unknown)
@@ -271,7 +271,7 @@ template<class Allocator>
 template<class String>
 void
 basic_fields<Allocator>::reader::
-prepare(String& s,basic_fields const& f,
+prepare(String& s, basic_fields const&,
     unsigned version, unsigned code)
 {
     if(version == 11)

include/beast/http/impl/read.ipp

@@ -318,7 +318,7 @@ class read_msg_op
         message_type& m;
         parser_type p;
 
-        data(Handler& handler, Stream& s_,
+        data(Handler&, Stream& s_,
                 DynamicBuffer& b_, message_type& m_)
             : s(s_)
             , b(b_)

include/beast/http/impl/write.ipp

@@ -358,7 +358,7 @@ class write_msg_op
         serializer<isRequest,
             Body, Fields, no_chunk_decorator> sr;
 
-        data(Handler& h, Stream& s_, message<
+        data(Handler&, Stream& s_, message<
                 isRequest, Body, Fields>& m_)
             : s(s_)
             , sr(m_, no_chunk_decorator{})