kvm_swap: ksw_devname too short

kvm_swap.ksw_devname is defined in <kvm.h> as 32 characters. It's easy to
exceed this (e.g. /dev/diskid/DISK-4C441001130129435304p2)

I suppose setting an automatic glabel would be the solution, but how much
hassle would bumping this field cause? I notice that swap with such long
names still actually works...

Cheers