Add optimization to move mrg_uniform to the GPU.
Fix the GPUA version of MRG to use the same rstate shape as the CPU one.
Add an optimization to move mrg_uniform to the GPU.

While there fix the inplace optimization so that it actually works with the GPU versions.
Fix a typo in Kernel that hasn't caused problems (yet) because 'None' is a valie C identifier.
Merge pull request #1845 from abergeron/gpua_rng_opt

Gpua rng opt