Update runtime files

runtime/ftplugin/dune.vim

@@ -0,0 +1,20 @@
+" Language:    Dune buildsystem
+" Maintainer:  Markus Mottl        <markus.mottl@gmail.com>
+"              Anton Kochkov       <anton.kochkov@gmail.com>
+" URL:         https://github.com/rgrinberg/vim-ocaml
+" Last Change:
+"              2018 Nov 3 - Added commentstring (Markus Mottl)
+"              2017 Sep 6 - Initial version (Etienne Millon)
+
+if exists("b:did_ftplugin")
+  finish
+endif
+let b:did_ftplugin=1
+
+set lisp
+
+" Comment string
+setl commentstring=;\ %s
+setl comments=:;
+
+setl iskeyword+=#,?,.,/