- fixed compilation error in operator= - added copy constructor
- fixed compilation error in operator=
- added copy constructor

[git-p4: depot-paths = "//sw/gpgpu/nvbio/main/": change = 18496229]

NVlabs/nvbio,kimrutherford/nvbio,NVlabs/nvbio,NVlabs/nvbio,NVlabs/nvbio,kimrutherford/nvbio,kimrutherford/nvbio,kimrutherford/nvbio