New buffers() replaces to_string() (API Change):

A new function, buffers(), returns an implementation defined object
which wraps a ConstBufferSequence and supports formatting to a
std::ostream.

The function to_string is removed, as the new implementation allows
conversion to string using boost::lexical_cast on the return value
of the call to buffers(). Streaming to an output stream is more
efficient: no dynamic allocations are performed.

Example:

    streambuf sb;
    std::cout << buffers(sb.data()) << std::endl;

test/http/parser_bench.cpp

@@ -10,9 +10,10 @@
 
 #include <beast/http.hpp>
 #include <beast/core/consuming_buffers.hpp>
+#include <beast/core/ostream.hpp>
 #include <beast/core/streambuf.hpp>
-#include <beast/core/to_string.hpp>
 #include <beast/unit_test/suite.hpp>
+#include <boost/lexical_cast.hpp>
 #include <chrono>
 #include <iostream>
 #include <vector>
@@ -31,6 +32,15 @@ public:
     corpus cres_;
     std::size_t size_ = 0;
 
+    template<class ConstBufferSequence>
+    static
+    std::string
+    to_string(ConstBufferSequence const& bs)
+    {
+        return boost::lexical_cast<
+            std::string>(buffers(bs));
+    }
+
     parser_bench_test()
     {
         creq_ = build_corpus(N/2, std::true_type{});