Add buffer_size

doc/qbk/03_core/4_buffers.qbk

@@ -20,6 +20,14 @@ transferred.
 
 [table Buffer Algorithms and Types
 [[Name][Description]]
+[[
+    [link beast.ref.boost__beast__buffer_size `buffer_size`]
+][
+    This is a more reliable version of
+    [@boost:/doc/html/boost_asio/reference/buffer_size.html `net::buffer_size`]
+    which is easier to use and also works for types which are convertible
+    to `net::const_buffer` or `net::mutable_buffer`.
+]]
 [[
     [link beast.ref.boost__beast__buffers_cat `buffers_cat`]
 ][

doc/qbk/quickref.xml

@@ -66,6 +66,7 @@
           <member><link linkend="beast.ref.boost__beast__bind_back_handler">bind_back_handler</link>&nbsp;<emphasis role="green">&#128946;</emphasis></member>
           <member><link linkend="beast.ref.boost__beast__bind_front_handler">bind_front_handler</link>&nbsp;<emphasis role="green">&#128946;</emphasis></member>
           <member><link linkend="beast.ref.boost__beast__bind_handler">bind_handler</link></member>
+          <member><link linkend="beast.ref.boost__beast__buffer_size">buffer_size</link>&nbsp;<emphasis role="green">&#128946;</emphasis></member>
           <member><link linkend="beast.ref.boost__beast__close_socket">close_socket</link>&nbsp;<emphasis role="green">&#128946;</emphasis></member>
           <member><link linkend="beast.ref.boost__beast__generic_category">generic_category</link></member>
           <member><link linkend="beast.ref.boost__beast__get_lowest_layer">get_lowest_layer</link>&nbsp;<emphasis role="green">&#128946;</emphasis></member>