clow: lower-level wrappers around cudarc structures

This library wraps around some key structures of Cudarc. Key features are type-safe device pointer types and fat-pointer types, as well as an alternative to cudarc's CudaSlice struct that does not contain any event tracking logic at all.

Why?

For certain applications, we need to be able to shove pointers to GPU memory onto the GPU as-is, many of which require that a device pointers lifetime cannot be constrained to a local Rust scope. This clashes with the event-tracking and SyncOnDrop logic in Cudarc. The alternative types that Clow provides, work on a lower level than the Cudarc alternatives and allow more flexibility. For example, Clow's ClowView has an internal layout that matches a fat pointer, whereas Cudarc's CudaView has a layout that cannot be broken down to a simple 16-byte pointer value.

Versioning

Make sure the Cudarc version matches; otherwise Cudarc will probably fail to compile against your local architecture.