printf() has standard flag for adding "0x" prefix before hexadecimal integer.

MOD='[-+]\?[0-9]*.\?[0-9]*[lL]*'
git grep -l "0x%${MOD}x" | xargs -n1 sed -e "s/0x%\(${MOD}\)x/%#\1x/g" -i
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>