Rename concept to DynamicBuffer (API change):

Conform to the Networking TS by renaming the Streambuf concept
to DynamicBuffer in all places. Values of types meeting the
requirements of DynamicBuffer are renamed to dynabuf.

See:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4478.html#requirements.dynamic_buffers

* Headers renamed
* Formal parameter names renamed
* Template argument types renamed
* Documentation updated

include/beast/core/write_dynabuf.hpp

@@ -0,0 +1,63 @@
+//
+// Copyright (c) 2013-2016 Vinnie Falco (vinnie dot falco at gmail dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#ifndef BEAST_WRITE_DYNABUF_HPP
+#define BEAST_WRITE_DYNABUF_HPP
+
+#include <beast/core/buffer_concepts.hpp>
+#include <beast/core/detail/write_dynabuf.hpp>
+#include <type_traits>
+#include <utility>
+
+namespace beast {
+
+/** Write to a @b `DynamicBuffer`.
+
+    This function appends the serialized representation of each provided
+    argument into the dynamic buffer. It is capable of converting the
+    following types of arguments:
+
+    @li `boost::asio::const_buffer`
+
+    @li `boost::asio::mutable_buffer`
+
+    @li A type meeting the requirements of @b `ConvertibleToConstBuffer`
+
+    @li A type meeting the requirements of @b `ConstBufferSequence`
+
+    @li A type meeting the requirements of @b `MutableBufferSequence`
+
+    For all types not listed above, the function will invoke
+    `boost::lexical_cast` on the argument in an attempt to convert to
+    a string, which is then appended to the dynamic buffer.
+
+    When this function serializes numbers, it converts them to
+    their text representation as if by a call to `std::to_string`.
+
+    @param dynabuf The dynamic buffer to write to.
+
+    @param args A list of one or more arguments to write.
+
+    @throws unspecified Any exceptions thrown by `boost::lexical_cast`.
+
+    @note This function participates in overload resolution only if
+    the `dynabuf` parameter meets the requirements of @b `DynamicBuffer`.
+*/
+template<class DynamicBuffer, class... Args>
+#if GENERATING_DOCS
+void
+#else
+typename std::enable_if<is_DynamicBuffer<DynamicBuffer>::value>::type
+#endif
+write(DynamicBuffer& dynabuf, Args const&... args)
+{
+    detail::write_dynabuf(dynabuf, args...);
+}
+
+} // beast
+
+#endif