vmstat: sys variables are unsigned longs

vmstat: sys variables are unsigned longs

When the API changed for the use_format the type changed for the
system variables out of stat, but the printf format was not changed
along with it.

vmstat.c:868:14: warning: format ‘%lld’ expects argument of type ‘long
long int’, but argument 2 has type ‘long unsigned int’ [-Wformat=]
     printf(_("%13lld interrupts\n"), SYSv(sstat_INT));

References:
 commit 2e6435a39dd8260462652b999c1bb45e15ae0d62

Signed-off-by: Craig Small <csmall@dropbear.xyz>