Integrate Linenoise into Kiln for REPL support.

[toroidal-code]

I have written the glue OCaml code for this using CTypes, it will be distributed as a OPAM package, which we can link against.

[toroidal-code]

Status: finished writing the linenoise wrapper. It will not be able to be submitted until the OPAM package for Ctypes is updated (I'm using stubs, which aren't yet released)