Support GHCJS compilation

**Is your feature request related to a problem? Please describe.**
GHCJS cannot compile `accelerate`.

**Describe the solution you'd like**
GHCJS to successfully compile `accelerate`.

**Describe alternatives you've considered**
Don't use `accelerate`.

**Additional context**
`accelerate` currently uses foreign C calls that fail under GHCJS. Additionally, the `terminal-size` dependency does not compile with GHCJS.

I'm not sure how practical it would be to support compilation under GHCJS, but it would make `accelerate` an even more backend agnostic framework for computation. With GHCJS, `accelerate` could run on the web, in addition to CPUs and GPUs.