Added the CUDA backend's version of an Accelerate FFI.
Haddock wibbles.
Used more descriptive names and added haddock comments to inContext and inDefaultContext.
Changed to match new ForeignFun definition. Also more haddock wibbles.
Changed backend representation to use CIO instead of IO. Also removed tuple conversion of DevicePtrs.
Merge pull request #3 from robeverest/master

An FFI for the CUDA backend.