vl_svmtrain.m: fix doc (in current code, SDCA is default)
vl_svmtrain.m: fix doc (in current code, SDCA is default)

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