Add GPU acceleration

[mborland]

Now that the CUDAfication of math is underway many of the same techniques can be applied here to enable CUDA and SYCL support throughout the library. The main point of difficulty for SYCL will be removing recursion from the constructors of the non-fast types.

[mborland]

spir64-unknown-unknown aka SYCL does not support 128-bit integer types even thought the host compiler (ICPX) does. Need to add additional macro checks.

[mborland]

Deferred for now. Development will exist on cuda-development branch. Maybe for version 3 post-boost review or when we receive a strong demand signal