Buffers have a feature table.

Closes #891

include/boost/beast/core/static_buffer.hpp

@@ -143,11 +143,10 @@ public:
     /** Returns a mutable buffer sequence representing writable bytes.
 
         Returns a mutable buffer sequence representing the writable
-        bytes containing exactly `n` bytes of storage. Memory may be
-        reallocated as needed.
+        bytes containing exactly `n` bytes of storage.
 
         All buffers sequences previously obtained using
-        @ref data or @ref prepare are invalidated.
+        @ref data or @ref prepare may be invalidated.
 
         @param n The desired number of bytes in the returned buffer
         sequence.