vl_roc.m: fixes typos
vl_roc.m: fixes typos

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