Temporary: fix locations in optarg desugaring
Temporary: fix locations in optarg desugaring

dra27/merlin,fxfactorial/merlin,dra27/merlin,neojski/merlin,haselwarter/merlin,fxfactorial/merlin,dra27/merlin,the-lambda-church/merlin,chambart/merlin,dra27/merlin,rgrinberg/merlin,neojski/merlin,fxfactorial/merlin,neojski/merlin,ocaml/merlin,rgrinberg/merlin,rgrinberg/merlin,ocaml/merlin,haselwarter/merlin,fxfactorial/merlin,chriskonstad/merlin,haselwarter/merlin,the-lambda-church/merlin,chambart/merlin,chriskonstad/merlin,ocaml/merlin,neojski/merlin,rgrinberg/merlin,haselwarter/merlin,ocaml/merlin,chambart/merlin,chambart/merlin,the-lambda-church/merlin