Fix Windows paths canonicalization (#1254)
Fix Windows paths canonicalization (#1254)

* Use system separator after drive letter
ocaml/merlin,rgrinberg/merlin,rgrinberg/merlin,ocaml/merlin,dra27/merlin,ocaml/merlin,rgrinberg/merlin,rgrinberg/merlin,the-lambda-church/merlin,the-lambda-church/merlin,the-lambda-church/merlin,ocaml/merlin,dra27/merlin,dra27/merlin,dra27/merlin