Newly added heap buffer create interface can create a
large enough buffer whose backup memory can increase
dynamically as needed.

Reviewed-by: Vasily Khoruzhick <anarsoul@gmail.com>
Tested-by: Andreas Baierl <ichgeh@imkreisrum.de>
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Part-of: <!3264>