sift: fixed overflow bug causing crashes on some architectures
sift: fixed overflow bug causing crashes on some architectures

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