vl_binsum.c: improves error messages
vl_binsum.c: improves error messages

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