clang complains:
> clang -g -O2 -Wall -Werror -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0  -iquote ../lib/arch/x86/include -I../lib   groups.c ../lib/libzdtmtst.a ../lib/libzdtmtst.a -o groups
> groups.c:22:9: error: comparison of unsigned expression < 0 is always false [-Werror,-Wtautological-compare]
>         if (ng < 0) {
>             ~~ ^ ~

Declare ng as int.
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>