vl_covdet.m: improves doc
vl_covdet.m: improves doc

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