vsprintf: Fix <sys/string.h> include on Novena
vsprintf: Fix <sys/string.h> include on Novena

This file does not exist.  Include <string.h> instead.

Signed-off-by: Sean Cross <dd28e116ed3e781f3ae781acae9fb18383f35c2f@kosagi.com>

mandl/fernly,xobs/fernly,mandl/fernly,pfalcon/fernly,mandl/fernly,pfalcon/fernly,xobs/fernly,urjaman/fernly,urjaman/fernly,urjaman/fernly