define the to_const meta-function for PackedStreamRef
define the to_const meta-function for PackedStreamRef

[git-p4: depot-paths = "//sw/gpgpu/nvbio/main/": change = 18426879]

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