vl/kdtree.c: fixes a bug for which clusters of identical values would cause the tree construction to crash
vl/kdtree.c: fixes a bug for which clusters of identical values would cause the tree construction to crash

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