Remove compiler warning.
Remove compiler warning.

/Users/martin/OpenSC/OpenSC.tokend/Tokend/DbValue.cpp:237:11:{237:6-237:10}{237:13-237:14}: warning: comparison of unsigned expression < 0 is always false [-Wtautological-compare,3]
         if (hour < 0 || hour > 23)
             ~~~~ ^ ~
/Users/martin/OpenSC/OpenSC.tokend/Tokend/DbValue.cpp:241:13:{241:6-241:12}{241:15-241:16}: warning: comparison of unsigned expression < 0 is always false [-Wtautological-compare,3]
         if (minute < 0 || minute > 59)
             ~~~~~~ ^ ~
/Users/martin/OpenSC/OpenSC.tokend/Tokend/DbValue.cpp:245:13:{245:6-245:12}{245:15-245:16}: warning: comparison of unsigned expression < 0 is always false [-Wtautological-compare,3]
         if (second < 0 || second > 59)
             ~~~~~~ ^ ~

dirkx/OpenSC.tokend,dirkx/OpenSC.tokend,dirkx/OpenSC.tokend,dirkx/OpenSC.tokend,dirkx/OpenSC.tokend,dirkx/OpenSC.tokend