make sure int8 is signed on all platforms
make sure int8 is signed on all platforms

[git-p4: depot-paths = "//sw/gpgpu/nvbio/main/": change = 18790849]

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