add .data() member to Diagonal<>
add .data() member to Diagonal<>

TSC21/Eigen,toastedcrumpets/eigen,TSC21/Eigen,ritsu1228/eigen,ritsu1228/eigen,ritsu1228/eigen,TSC21/Eigen,pasuka/eigen,toastedcrumpets/eigen,pasuka/eigen,ROCmSoftwarePlatform/hipeigen,pasuka/eigen,Zefz/eigen,pasuka/eigen,ROCmSoftwarePlatform/hipeigen,ritsu1228/eigen,toastedcrumpets/eigen,toastedcrumpets/eigen,TSC21/Eigen,Zefz/eigen,Zefz/eigen,ROCmSoftwarePlatform/hipeigen,pasuka/eigen,Zefz/eigen,ROCmSoftwarePlatform/hipeigen,ritsu1228/eigen