hikmeans: fix signed / unsigned comparison warning
hikmeans: fix signed / unsigned comparison warning

vlfeat/vlfeat,WangDequan/vlfeat,erexhepa/vlfeat,richarddzh/vlfeat,qubick/vlfeat,j-bo/vlfeat,mylxiaoyi/vlfeat,vlfeat/vlfeat,CansenJIANG/vlfeat,erexhepa/vlfeat,rxl194/vlfeat,vlfeat/vlfeat,hongzhili/vlfeat,cvfish/vlfeat,cvfish/vlfeat,cvfish/vlfeat,j-bo/vlfeat,erexhepa/vlfeat,rxl194/vlfeat,richarddzh/vlfeat,j-bo/vlfeat,CansenJIANG/vlfeat,mylxiaoyi/vlfeat,richarddzh/vlfeat,cvfish/vlfeat,erexhepa/vlfeat,CansenJIANG/vlfeat,CansenJIANG/vlfeat,rxl194/vlfeat,vlfeat/vlfeat,CansenJIANG/vlfeat,mylxiaoyi/vlfeat,j-bo/vlfeat,mylxiaoyi/vlfeat,j-bo/vlfeat,hongzhili/vlfeat,erexhepa/vlfeat,richarddzh/vlfeat,hongzhili/vlfeat,mylxiaoyi/vlfeat,richarddzh/vlfeat,qubick/vlfeat,cvfish/vlfeat,vlfeat/vlfeat,cvfish/vlfeat,erexhepa/vlfeat,rxl194/vlfeat,WangDequan/vlfeat,WangDequan/vlfeat,qubick/vlfeat,rxl194/vlfeat,rxl194/vlfeat,hongzhili/vlfeat,mylxiaoyi/vlfeat,hongzhili/vlfeat,vlfeat/vlfeat,WangDequan/vlfeat,richarddzh/vlfeat,CansenJIANG/vlfeat,WangDequan/vlfeat,qubick/vlfeat,qubick/vlfeat,WangDequan/vlfeat,hongzhili/vlfeat,qubick/vlfeat