changing change log for new memory allocator

Docs/manual.texi

@@ -48936,6 +48936,9 @@ Our TODO section contains what we plan to have in 4.0. @xref{TODO MySQL 4.0}.
 
 @itemize @bullet
 @item
+Strategy of memory allocation of 'root memory' is changed. Block size grow 
+with number of allocated blocks.
+@item
 Fix @code{SQL_CALC_FOUND_ROWS} to work with @code{UNION}s. It will work only
 if the first @code{SELECT} has this option and if there is global @code{LIMIT}
 for the entire statement. For the moment, this requires using parentheses for