sift.c: improved commment
sift.c: improved commment

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