webdoc.py: improve index generation
webdoc.py: improve index generation

Previously, only <a> tags would get the class=‘active’ attribute in generated indexes; Now the same attribute is applied to the containing <li> element too.

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