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/chunk_encode.cpp

@@ -8,8 +8,9 @@
 // Test that header file is self-contained.
 #include <beast/http/chunk_encode.hpp>
 
-#include <beast/core/to_string.hpp>
+#include <beast/core/ostream.hpp>
 #include <beast/unit_test/suite.hpp>
+#include <boost/lexical_cast.hpp>
 
 namespace beast {
 namespace http {
@@ -30,6 +31,15 @@ public:
         }
     };
 
+    template<class ConstBufferSequence>
+    static
+    std::string
+    to_string(ConstBufferSequence const& bs)
+    {
+        return boost::lexical_cast<
+            std::string>(buffers(bs));
+    }
+
     static
     void
     encode1(std::string& s, final_chunk const& fc)