Consider using sized integer types for the builtins

[eyalroz]

While nVIDIA's own C headers for builtin wrappers use the fundamental types int, unsigned, unsigned long long etc. - the builtins are actually based on exact parameter sizes, not the wishy-washy C integer types. Should we then not make our builtins reflect that, by taking only intNN_t's and uintNN_ts as integer parameters?